Hi guys. I've recently bought myself a B34-2 project bike. I've been lurking in the forum for a while, reading other helpful posts and so I thought I might do a bit of a blog as I bring my bike back to life.
Hopefully you'll be able to help me with some tips along the way and also maybe someone else might find it useful to learn from my mistakes along the way!
I'm new to bikes of this era. The oldest bike I've owned or ridden is my '72 Suzuki, but having enjoyed how much more raw and simple that experience was compared to the more modern bikes I've owned, I thought I might like to take that a step further and try an old British single out. I was looking at post war bikes, but then the more research I did, the more I was fascinated with the idea of a 'really' old bike.
I had been looking at bigger, more powerful bikes but when I saw this little B2 come up in need of some love and attention, the heart said 'this is the one'. I liked that it had all the antiquated features I thought would be interesting to experience, like the girder forks, rigid frame and hand change, and with an OHV engine in a much more affordable package than many other bikes with that feature set. It seemed a good way to dip my toe in the water!
The bike clearly needs a lot of work. Initial thoughts of doing a bit of recommissioning and getting out on the road, have predictably instead turned to a full rebuild. I'm not doing a concourse restoration, more of an oily rag rebuild. I want it to be mechanically spot on, but cosmetically will leave the patina and age on the components. This bike has either had quite a few parts swapped about, or it's been assembled from parts, and with no providence I don't think there's any reason to get too hung up on originality. I will try to keep it feeling 'period correct' though.
Attached are a couple of pictures of the bike as it was delivered to me, and yes I did finally get round to cutting the lawn shortly after!
The exhaust is obviously not standard, but stylistically I don't mind it, so it can stay for now. The tank I believe should have been the nickel plated type, with the green inlays? The green it is currently is poorly brush painted, so definitely not original. I'm crossing my fingers for old patinated nickel left under that paint!
The front wheel is wrong, its got a WM2 rim with the wrong spoke lengths as the rim is offset in the forks, or the whole front wheel is from a different bike? I don't mind the wider front rim, but having the front wider than the back could make for strange handling I'm sure. I'll cross that bridge later.
Before worrying about any of that though, my initial concerns are with the frame, engine and gearbox...
This is the one Andy Tiernan had for sale a few months ago, isn't it? I was tempted by this at the time as I'd been looking for one for a while, but found one in the end elsewhere. I remember the bungee cord kickstart return too! I'll be interested to see how you get on.
Despite having one, I've very limited knowledge of them, but if I can help with sending pictures of anything you're not sure of let me know. I've also got a memory stick with pictures of the restoration of mine before I bought it, so there might be something on there that could help too. I've not actually looked yet and the bike is away getting checked over by someone currently.
I don't do facebook, but some of the groups on there can be quite helpful as well as this forum.
I've had a couple of rides on mine and loved it. What area are you? I'm Chichester.
All the best!
Who designed that engine?
Best of luck with the rebuild/restoration. By the way BSA used nickle plating up to 1929 and by 1930 bikes were a mixture of nickle and chrome plating (BSA never wasted anything and used up old nickle plate stock) but by 1931 and thereafter all bright parts were chrome plated.
Yes, thats the one @courtney. It's nice to know I wasn't the only one silly enough to be interested in buying it! haha. Thank you for the offer of pictures to help, I may well have to take you up on that at some point. I'm not a Facebook person either, I'd much rather use a forum.
Obviously I'm yet to do anything more than sit on mine and imagine a ride, but I'm excited to see what it's all about!
Can't help you there @MGI! Maybe someone with more BSA knowledge knows? I do know this engine is a bit old fashioned even for the time by still using total loss oiling. Does make it nice and simple though!
That's interesting to know @Y13 Alan G. I had read online about the nickel tanks, but didn't know about the switch to chrome. Shame really, nickel plating has something subtle different about it to chrome that just looks nice.
It was a couple of months ago now that I got the bike, and as I eluded to in the first post I have made a start. It only took one evening pull it all to pieces, but as I did I could see that the rear end of the frame and centre stand were all a bit twisted.
Thankfully, as the rear frame sections are all bolt on it's not as big a deal as a welded together frame might be. With the help of a laser level and a whole lot of measuring, I'm pretty confident I've managed to tweak the frame back into line.
What I did discover is that my bike is fitted with the wrong 'back stays' as the parts manual calls them, or seat stays as I'd call it from my mountain biking days. The B2 should have a piece of flat bar joining the two, whereas mine is tubular. Hopefully the dimensions of what is fitted to mine are similar enough as to not change the geometry of the frame!
I'm still deciding whether my centre stand, which has had previous repairs and is rust damaged, is worth trying to save or whether I should keep my eyes open for a replacement.
The gearbox was next. As was noticed in the first post, the kick start was being held up with a bungee cord, as the spring was missing.
In my naivety to boxes of this age, I took the box apart looking for a broken spring internally... only to realise that it uses an external spring! Haha, oh well. It gave me chance to check over the innards of the gearbox anyway, most f which look nice and healthy. The kickstart pinion doesn't look great though, possibly as a result, of the missing spring allowing the lever to catch the spinning gearbox at speed? Or maybe it's just normal wear. Either way, the kickstarter was engaging fine before I took the box apart, so I've just left it alone for now.
I found evidence of welding to the gearbox casing, maybe as a result of the same incident that cause the bend in the chain stays at the back of the frame and the need for a replacement back stay do we think? I also spotted another crack which had not been dealt with, so broke the welder out and sorted that out now.
I purchased a kickstart spring from Draganfly, which I knew wasn't quite the right one but the measurements sounded close to the original. Sadly it didn't fit right, so I had to do some modifications. Works fine on the bench, how long it lasts in regular use on the road, we will have to see!
The gearbox is now back together, filled with a fresh charge of Castrol D and ready to go back in the frame, but first I need to look at the engine...
A few random thoughts, which may or may not be helpful. It all depends on what you want to do with the B2.
I imagine the gearbox had split because the kickstart stop had become loose a few times over the last 90 years, and the motorcycle had probably fallen over onto the kickstart a few times. The stop does tend to come loose, so keep an eye on it. You should fit a rubber sleeve over it with a steel outer (like a silent bloc bush) otherwise the rubber will only last a few weeks.
I know it's too late now, but mainshaft and layshaft endfloat are critical for a good gearchange. If you ever dismantle the gearbox again, you might want to fit a sealed bearing to reduce oil leaks. One of the problems is that the layshaft is often slightly bent, which makes setting endfloat nearly impossible.
Your kickstart ratchet pinion is very badly worn. I've not seen a worse one, and you may find that it either slips or jams in use, although the quadrant looks to be in quite good condition. I would try to find a new one as a matter of urgency.
Cam wear on B2's seem to be quite high, so it might be worth checking how far the valves open. I eventually found mine were only opening 1/8".
If you split the flywheels, note there are a pair of con rod thrust washers on the flywheels with chamfers on them. They can be drifted out through holes on the outer faces of the flywheels. They must be fitted with the chamfers in a certain position. The chamfers allow more oil into the big end. Oiling is splash only. There is no feed to the big end. It would be very worthwhile getting hold of a copy of Bruce Main Smiths green book of BSA's 1935 to 1940, in which he shows the position of the chamfers, and many other things.
You will probably find the unbushed little end is badly worn. Alpha Bearings can bore out the eye and fit a thin wall bush if required.
Your petrol tank with the raised ovals, is from a later machine. Yours would have had threaded oil and petrol filler holes and alloy caps. But as long as it doesn't leak.............
The original advance/retard would have been a twistgrip on the left handlebar. The bar would have been slotted to accommodate it.
Replica twist grips are available from Cornucopia in Germany, but they are made up of a lot of parts and are quite expensive. So you may want to fit a lever control for the time being. There would also have been a valve lifter fitted as part of the original clutch lever. These levers turn up on ebay every now and then, but again, they are prohibitively expensive.
I think your backstays may be from a Blue Star Junior, but as long as it all lines up...........
Carburettor settings, Main jet 75, needle jet .106, slide 4/4, needle position 2.
I set my pilgrim pump to 1 drop every 3 or 4 seconds.
Terry's valve springs are part no. VS 22.
The Maglita is a very wonderful instrument. Set points between 0.010" and 0.012" and see which is best for starting. If you're lucky it should produce about 2 Amps unregulated. Your headlamp switch should have an "off" position as a 2A charge on a long run may strain an AGM battery. They don't like it up 'em.
I set my maximum ignition advance to 35 degrees BTDC which seems to give good results. Spark plug gap 0.018" or 0.015 if it gives better starting. I highly recommend checking your valve timing figures against BSA's figures. After all, every little helps.
Finally, I believe the engine would have been designed by a fellow called Harold Briggs, who was BSA's Chief Designer in the '30's before Val Page took over.
Let us know how you get on.
Just to clarify what I wrote about the headlamp switch, it should have a 'C' for charge position, so charging (if any) can be switched on or off.
Re the centre stand, these were notorious for rotting away. You will find that a C10 centre stand (29-4860) will fit, but you will have to drill the stand legs and fit 2 short pegs to act as stops. They often turn up on ebay, and are also available from dealers, but quite expensive.
Thanks for all that information Steve, really helpful!
I'm more than happy to pull my gearbox apart again if it's going to result in a better change :) Since reading your post I've found service sheet 46 mentions a 0.004" clearance when fitting a new mainsheet or layshaft bush, is that correct?
I could see the kickstart pinion was really badly worn but, as I said, the bike seemed to kick over 'ok' before I took it apart. When I had looked online the part seemed hard to find in good condition and other people said they were using clearly damaged ones. Your post prompted me to have another look though, and I spotted a NOS one on eBay. So have just purchased that and will swap it in when investigating the end float.
The kickstart stop is definitely just a bare metal pin, so will look for something to pad that with!
Regarding the engine, I'm just on the disassembly and investigation stage, so again thank you for all the helpful pointers. What I do know so far is that the big end and little end both have play in them. There big end is just a tiny amount, the small end is more.
I have split the flywheels and I think the big end will be ok with just some new rollers, as I understand it it should have 1 row of 1/4" x 1/2" rollers, mine had 2 rows of 1/4" x 1/4" rollers currently and they are worn and measuring 0.2480-0.2485" diameter. I test fitted some new standard size rollers and it felt much better. The big end bearing surface inside the con rod doesn't look marvellous, but then it's 90 years old? I don't know if this light pitting/marking is disastrous or not. I can't feel it with a finger nail or anything and it feels smooth when assembled. I think it's worth a shot to just assemble it and see how it goes personally. Picture attached, happy to be corrected!
Thank you for the notes of the thrust washers, I can see mine have a reasonable step worn into them, so I should look into replacing them. There did appear to be quite a lot of side to side movement in the big end. It's interesting seeing how the oiling was made to work, it's quite familiar to me from 2 strokes really. Much more so than if I was used to modern 4 stroke oiling.
Thank you for the recommendation of someone who can help with bushing the small end. I'm also looking into whether I can find a just slightly oversize gudgeon pin, and ream out the little end eye and piston to suit? I do like to find ways to do these things myself if possible, and am planning on purchasing a lathe to expend my skills and help with this project.
The cams look 'ok' to me, I've seen wiped out cam lobes before, and this doesn't look like that. Do you know what the original valve lift should have been? I've got approx 0.200" at the cam.
The piston is a +60 Hepolite 7151. I'm not sure what, if any, the difference is between this and the 7150 I see more often suggested as fitting the B2?
Piston to bore clearance is good, the ring gaps are not! The top ring is badly filed and the ring gap is too tight, only 0.005", and the 2nd ring and oil scraper look like they are much older or just plain wrong as the ring gap is almost 0.060"!! New rings are in the post...
I notice the original piston in the parts book was not fitted with an oil scraper, just 2 compression rings. It it a good modernisation to run with the oil scraper ring? Or would it interfere with how the oil was designed to be burnt off in this total loss system, and should therefore be omitted?
That's a shame about the tank. I will probably find a way to pay homage to what the original paint scheme should have been, rather than stick with the all green then. In terms of getting out riding though, yes the tank is a good one. Bit dirty inside but not rusty and no leaks.
Looking in the parts book, I agree, the rear stays do closely resemble the B3 model. The rear end bolts up ok (now I've straightened the lower arms out!) so I'll run with it!
On the electrics front, given how useless I find the pair of 35w bulbs in my '60s Fiat when faced with any kind of oncoming traffic, I'd presumed that a single 12/18w headlamp bulb on this bike would make night riding exceedingly difficult! With that in mind, and given that the bike has a cheap modern replica headlight unit fitted (with just 3 switch positions, no 'C' option), I was planning to run in 'daylight' trim and not fit lights, at least to start with.
A brake light might be nice though, just to deal with modern traffic! Is it safe/possible to use the power generated from the Maglita without a battery? In this case just connecting it to a brake light circuit as and when it's needed? If not I'll just disconnect the charging system and sort a standalone brake light system with a little rechargeable battery pack.
I've got an ebay bargain £10 C11 centre stand in the post (29-4883 I believe), so I'll see if that can be modified to fit. :)
So glad you have managed to source a ratchet pinion. Let's hope it's the right one, as there are many of them and they all look much the same.
When you first posted, I was going to suggest you got it running and tried it out on the road, to see what was what and deal with each problem as it arose.
But, by then you had already stripped it down. So you have a big decision to make. If you go for a full restoration, it will cost many thousands of pounds.
For example, if you got the correct tank...and they do turn up on ebay, it will cost you about £1500 to have polished, leak tested, triple plated, painted and lined. Then you are committed to making the rest of the bike looking like the tank. I think the approach is to do the minimum. You say the kickstart works OK. So why not leave it? Should it fail in the future, you have a new part in stock. Again, regarding endfloat (0.004" sounds about right, but you can't get better than a service sheet), maybe all the gears select OK as it is.
The tank is not dissimilar to the correct one, so maybe you could spray the top of the tank silver and gold line it. You will get an idea of the layout from the parts book, which I assume you have?
I just use a bit of rubber tubing on the kickstart stop, encased in a steel outer, which you will be able to turn up on your new lathe! (If you decide to do the gearbox, you will be able to check the layshaft for straightness with a DTI gauge).
However, I feel that since the crankshaft is the heart of the engine I am prepared to bite the bullet and get it fully overhauled. After all, it will only be done once, and you'll never have to take the engine to pieces again. Alpha are superb engineers and are very familiar with this engine. They are quite quick, but it will cost a few hundred pounds. This would solve all your problems with little end wear, thrust washer wear, and big end uncertainties. Also, you won't have the difficulty in setting up the flywheels, unless you already have the equipment. The choice is entirely yours, but if you decide on repairs, a few thoughts: I have never seen the wear you describe on the thrust washers. I doubt if you will ever find new ones. Perhaps you could source some hardened steel washers of the correct dimensions from Bearing Suppliers, and grind a chamfer on them, but they do need to be an interference fit on the flywheel 'lip', and not turn.
I also think it will be very difficult to source a gudgeon pin that is the correct fit in the little end, which may be oval. Also, I think you will find the finish of the bore is appalling, with deep grooves in it. Also, bear in mind the clearances are minute, but perhaps I'm being pessimistic?
As a matter of interest, the little end on my motorcycle is very badly worn. It rattles a bit, but I'm ignoring it for the time being. You haven't said how bad yours is.
I suppose your big end doesn't look too bad, but an engineering shop would bore it out and rebush it. When you try oversize rollers, make sure everything is completely oil free and dry. Then, gird your loins, close your eyes, and turn the con rod slowly through 360 degrees a few times, to see if you can feel even the very slightest tightening and freeing of the con rod as it turns. If you can, then I'm afraid it won't last long. I have seen a few big ends with a double row of rollers. I think it may have been a modification.
I will post again later on, but briefly, I once had a NOS cam, and that gave 0.216" lift, so you're not far out.
The part number for the kickstart pinion is correct on the eBay listing, so I'm crossing my fingers!
Riding it and finding the problems along the way, was indeed plan A. Things just escalated haha. I'm definitely not doing a big money originality focused rebuild. This is just a case of making it run right and be safe and then get out riding.
I'm measuring the little end bore as 0.629" sideways and 0.635" vertically, I've got standard figure of 0.6250-0.6255". But I'm not entirely trusting of my accuracy of internal measurements on small diameters like that, I haven't got the right internal micrometer. The standard pin feels 'ok' side to side, so I think my measurements are over reading, but it does have some vertical movement.
I have to admit, I was presuming that any vertical little end movement was going to mean imminent disaster, and was one of the main reasons I decided to fully strip the engine. You can see the amount of movement at the crank here, and its 90% in the little end https://www.youtube.com/shorts/8bnaCPTe85A (https://www.youtube.com/shorts/8bnaCPTe85A)
The standard pin diameter is 0.6245", which is ~15.8mm, so I've got a 16mm diameter pin coming in the post, with the intention to try reaming the little end round again to suit this new pin and opening up the piston to suit. For a £20 fix, it's worth a shot, and if that fails, then maybe sending away to have it fixed properly will be the right move.
I've rebuilt several 2 stroke cranks of the same flywheel and pin design, so whilst I'm 'new' to pre-war bikes, this kind of work is not entirely new to me. I'm not expecting the flywheel truing to be too torturous on this one, single cylinder is much easier than the 2 cylinder crank I did most recently and unlike that crank this one doesn't need to rev to 10,000 rpm!
The bore isn't great, but I've seen worse. At +60 already, it would be a case of getting it lined to repair any damage, so in the mean time I'm hoping a light hone and new set of rings will get me out riding. I'll take some pictures next time I'm out in the shed.
Thats promising about the cam! Thank you.
I think you are very much on the right track with all this. I think the fact that you can strip an engine so quickly and easily, and also realign the flywheels is a great advantage. (I can't). As I said, my little end has rather a lot of play, but the engine runs fine....at the moment. I feel that if you reassembled it as it is, in practice it will be OK, but otherwise, I think your idea is a good one. We know that little end and big end clearances should be tiny. Your figures show half a thou limit. Precision engineers should look away now and 0.009" wear is massive, but on the other hand, precision costs a great deal of money and time. Under the circumstances, I think your approach is the right one, but others will violently disagree, and I can see their point. I've just seen your video, and yes, there is quite a lot of movement, but I'm sure your bigger pin will reduce it.
Pistons are a little confusing. I hope this is not too much information, but I have 2 undated sheets from Hepolite. One shows the 7151 piston as 6:1 compression, and the other shows 5.2:1 compression. 7151 has a flat crown with a slight chamfer and a compression height of 1", and mine has 2 compression rings and 1 oil control ring. 7150 also has a compression height of 1", and is quoted as for a B26 SV.
2725 has a compression height of 1 3/16" and has a "cone" crown. 5338 is a half dome piston and 3653 is a full dome piston, perhaps for running on methanol? (Well, why not? although your little end won't last long!)
I'm using a 2725 with no oil control ring, but for some reason I don't understand, I had to skim 1/8" off the bottom to clear the crankcase.
I'm sure an oil control ring is a good idea, and will not interfere with the oiling, but I see your point.
I too can't see the difference between the 7150 and 7151.
I think your approach to bore and piston is spot on, but if there is a ridge at the top of the bore, you might want to scrape it back to prevent the top ring from breaking.
BTW, you might want to invest in Radco's book "The Vintage Motorcyclists Workshop", a mine of useful information.
Tank colour would have been Mid Brunswick Green BS 226, rather than the Apple Green of yours, with a gold pinstripe between the paint and Chrome (or Silver paint).
I would get a repro Lucas MT 110 rear lamp, then you could get an LED "Lightboard" from Paul Goff to fit inside, which incorporates a stop light.
I see you have no battery or carrier. I made my carrier. It's not too difficult. You will need a hooter to be legal, but you could use a bulb horn, but I think the regulations state it must sound a continuous note.
I also use a clip on rechargeable bicycle LED rear light.
The repro headlight shells are very similar to the originals, but yours would have had a flat lavatory frosted glass, rather than a domed glass.
I have some info on the Maglita, but I'm not sure if it can be run without a battery. I'll have a look. But lets see if the Maglita is producing a charge first, and go from there. If you get caught out in the rain, you will probably want to switch the headlight on.
Lucas state that the Maglita can be run without a battery, but caution that high speeds should be avoided due to the risk of blowing bulbs due to high voltage. But you can obviously measure this. Remember also, that when the engine is ticking over, the points of the centrifugal cutout will be open, so the bulb will go out.
Thanks for all that info Steve. All interesting.
I was aware of the centrifugal cut out but didn't realise it wouldn't be engaged at idle. A fair point about being caught in the rain without lighting. I've got a reproduction MT110, it came with the bike, I was planning to modify it to use as my brake light.
I believe a bulb horn is fine as long as the bike was first used before 1973. https://www.gov.uk/guidance/mot-inspection-manual-for-motorcycles/7-audible-warning
Either way, plenty of time to mull that over and work out the electrical and legality bits and bobs. In the short term I've got rather more major mechanical issues to deal with! haha.
I think fitting the oil control ring is probably the right move, I think the main thing it might effect, if its limiting excess oil making it to the upper cylinder, is the amount of blue smoke if the pilgrim pump is set wrong? Time will tell.
Interesting about the different piston domes available. I'm sure the bike was designed to run on pretty poor quality fuel compared to a modern super unleaded (which I will be using for the lower ethanol content), so a mild bump in compression would do no harm I'm sure and gain a bit of performance. Still I'm getting ahead of myself, make do and mend what I have to get out and ride the bike has to be my first goal.
I have the 16mm gudgeon pin now, along with the appropriate reamer, I should get chance over the weekend to investigate the little end further, I will report back!
Should you ever decide to replace the ratchet gear, it's worth noting that the thin ring nut on the mainshaft with the 4 holes for a peg spanner is a left hand thread. I have a feeling that you probably already know this, but it might be useful for others.
Thank you for the heads up on the left hand thread, that is indeed news to me, so has saved me from certain head scratching in the garage.
I can report that I re-measured the wear on the small end, my previous measurements were over estimates I think. I've got a standard size from the Motorcycling magazine article of 0.6250-0.6255", and now I've remeasured I've come out at 0.626" sideways and 0.630" vertically. So 0.005" of vertical wear, less than the 0.009" I'd previously mis-measured.
I've carefully reamed the hole out on 0.630" all round, which suits the 0.629" (16mm) pin I'm using. I've only used fixed reamers before, and was using a cheap adjustable one this time, which I cannot recommend... but still the job is done. There's no vertical play any more, so thats great. There is a touch of 'rock' to the pin left, but it's a million miles better than it was.
I was able to ream the piston to match. It's possibly not quite as tight a fit on the pin as I might like, but there's no play and I'm sure it will be fine. Clearly this is a 'get me going' approach, and will likely be revisited in future.
While thinking of piston type issues, I re-inspected the bore and it was better than I remembered. A quick light DIY-hone to break the glaze and it's plenty useable.
I also received a new set of rings in the post. I couldn't find a spec for the ring gap for my bike, but did find specs for the C10 of 0.010". The C10 uses the same bore diameter and piston so that seemed as good a guess as any!
In a previous post I was wondering what the difference between the Hepolite 7150 and 7151 pistons was... the set of rings I have here for a 7150 have a 0.120" thickness oil scraper and my 7151 piston has a 0.160" oil scraper, so that might be the difference! I could hunt for a correct 7151 +60 oil scraper or, more probably given that no oil scraper was fitted originally, I shall just omit it for now and keep an eye on the amount of smoke.
In other news my new centre stand arrived in the post too, it's a 29-4883 which I believe is c11. I need to grind a bit of the casting away to allow it to fully fold up, but once that it done it's going to work nicely.
I've got a few more bits and bobs to sort on the engine side of things before it can start going back together, most importantly being that I need to machine a new cam bearing/bush as the inner one on my exhaust cam is spinning in the case. So I'm crossing my fingers someone buys my Daimler soon which will release the funds I need for a lathe!
One question, while I think of it, about the crank case breathing. I can see the crank case breathes through a passageway in the crank, which allows oil vapour to exit on to the drive sprocket and in turn lubricate the primary chain. From things I've read theres suggestion of a secondary breathing hole, possibly though the stud near the main bearing that holds the primary chain case? The stud on my bike here is solid, rather than hollow, have I misunderstood?
All sounds good to me.
I purchased some flanged oilite cam bushes from Brammer, Buck & Hickman. Part no. 213A7698. However, they have an OD of 3/4", so will need reducing to 11/16". Maybe you could try refitting yours with Loctite 648, but I would assemble the cam and timing cover while the loctite is hardening.
Well done solving the mystery of the 7150 and 7151 pistons.
BTW, while I remember, there should be a felt oil seal fitted into the deep recess of the crankcase hole for the crank shaft (if you see what I mean).
I think the stud you are referring to is the Primary Chain Oiler Stud, Part no. 29-584. This will have a hole drilled in it, to about half way, with a hole drilled at a right angle to allow oil to drop onto the primary chain. You can see what it looks like in the Parts Book. Maybe a previous owner had fitted a normal stud to stop oil from leaking out and oiled the primary chain before each run. Blocking the breather off will, of course, increase crankcase pressure.
Well, doesn't time fly! I've not had much chance to update, but progress has been made with my B2 rebuild.
I left off talking about the engine, which is now 90% done. Shortly after the last post I was able to purchase a lathe and learn the basics of using and and set about making some of the parts I needed.
Starting with the cases, I drilled out the broken remains of the lug for the primary chain oiler stud, turned up an aluminium plug and welded it in from behind. It could be a little prettier, but it was one of my first jobs on the lathe and will do the job perfectly well.
I also found that one of the threads for the studs for the barrel had been damaged, An oversize bolt jammed in there along with some liquid metal. Lovely stuff.... So I drilled that all out and made a custom stud that was larger on the case side but standard size to fit in the barrel.
I also fitted a new drive side bearing and made a new felt washer.
The last job on the cases was to make a new cam bushing up. After some careful measuring (thank you new micrometer set!) I decided that the case looks like it was close to standard size and that someone had fitted the 'wrong' cam bushing, which was about 0.010" too small OD.
It took a couple of attempts but I was able to turn up a bushing that I was happy with and then pressed it into the case.
Crank next. I drove the worn thrust washers off, flipped them over to give me a fresh surface and ground a new chamfer on to that side. A make do and mend solution, but one I think will work just fine.
Measuring the big end I found ~0.001" wear on the con rod, the crank pin came up standard size and the rollers themselves were 0.002" undersize. I purchased new rollers and wit the unit assembled it feels perfectly acceptable to me. The crank was the easiest one to reassemble I've done! It still took some patient hours of truing but it responded predictably and I was able to get it to within 0.0015" of true, which was good enough for me!
With that the bottom end could go together, and I could think about getting the piston and barrel on. I made some bronze gudgeon pin cushions to suit my 16mm piston pin. They are a little deeper than the originals to make up for the fact that the 16mm pin is 0.030" narrower than the standard pin.
That all went together smoothly with the new ring to the piston gapped to 0.010", I couldn't find a ring gap spec for the B2, but that was a spec for a C10 and seeing as it's the same piston, that seemed a good place to start.
I cut a new head gasket from a sheet of copper. The head gasket I removed (some sort of composite gasket?) was 1.5mm thick, so that's what I went for with the copper. In hindsight I wonder If I should have gone thinner for a mild compression bump... Easy enough to swap out, if I want, at a later date.
The head was the last major job for the engine. Thankfully the valve seats and the valves themselves looked pretty good, but the guides were quite worn. I turned up some new valve guides, and pressed them into the head.
The valve springs felt very soft to me, and I noticed that someone had put shims under the intake valve spring seat to try and increase the pressure! Lots of searching online with part numbers and I was able to score some NOS Terrys springs for a sidevalve B1, which have the same part number as the outer springs for the OHV B2. They certainly were an improvement over the springs that came o the bike. I re-used the old inner springs for now.
The rockers were thankfully in quite good condition. I stripped it all down, and removed some old carbonated up grease from the lubrication points, and was pleased to find no wear I the shatters or rockers themselves. The tip of the rocker, where it rides to the valve did have a little recent worn into it, but that was smoothed off in 5 mins with a diamond file.
And with that the engine is back together!
Wow. It's been a long time since I updated this. Progress has been made!
With and engine and gearbox on their way to being functional, the frame was next on my list. As I noted in the first post, the lines of the bike all looked a little of when I got it. Not unusual or surprising for a bike of it's age. As I was stripping the bike down it became quite obvious that the rear portion of the frame was not sitting right. The engine and gearbox are offset from the centreline of the bike, which doesn't help when visualising it, but even so the dropouts are clearly twisted to the right.
Helpfully, in this case, the rear chain stays and seat stays are all separate pieces that bolt on to the front half of the frame. This made getting things straight a much simpler job. With a laser level, lots of measuring and patience I slowly tweaked each piece till I was happy the rear wheel sat nice and straight and square to the centre line of the frame.
As mentioned earlier in this thread, I'd picked up a cast C10 stand to replace my original 30's fabricated one that had defintiyl seen batter days. With a little massaging from the angle grinder, it fits nicely and now the bike will stand up straight and I can have confidence the stand will be strong.
With that sorted out, the next obvious piece of the puzzle was the forks. They had felt 'ok' when I got the bike, and look to be straight. Once apart a few issues showed up though. Firstly, the holes in both the girders and steering head for the lower links were worn oval and allowing some movement. Not an easy thing to photograph, but they were 0.020-0.030" wider than they were tall.
So I drilled the holes out and made a set off bronze bushes up on the lathe, and pressed them in. It's now a good fit, possibly a touch on the tight side as there's a little drag turning the links, but I'm sure with a few miles that will loosen up and better that way than to start with slop already in the joint that will only get worse.
The second issue with the forks was that the spring was broken. I hadn't noticed at first, but the top couple of coils had fractured off from the rest. By wrapping the two halves of the spring together the previous owner had been able to keep it riding, but I'd rather a more elegant solution.
Finding a replacement spring has proved tricky. Being a lightweight bike, it's smaller than many of the other springs out there. Whilst I could modify the upper mount for a different spring, the lower mount is a spiral cast into the girder forks on to which the spring threads. So I need a spring on the same size, and also that its wound I the same direction. I did find a promising looking spring but it was wound the opposite way to mine so wouldn't have threaded on to the forks.
After some weeks of pondering it, I decided to clean up the broken end of the spring then make a new top mount, that properly fits the trimmed up wider end of the spring and also accounts for the loss of spring length so the forks sit at the right height.
But that's getting ahead of ourselves, before I started assembling bits the wheels had to be dealt with. Originally the bike would have had 19" WM1 rims front and rear on 19x3" tyres. The bike came to me with what I believe is the standard rear rim but the front rim was a WM2 front rim. Front rim wider than rear is likely to make for some interesting handling, so I knew I wanted to change one of the rims.
The rear rim turned out to be pretty rusty and also most of the appropriate style tyres suggest that you should have a wm2 rim for a 3" width, so the decision was made to go to wm2 rims from and rear.
Now hubs/brakes was the next piece of the puzzle. The rear hub seemed fine, a strip and regrease and all was ok. The brake seemed to be working fine, the drum surface wasn't amazing a bit rust pitted in places but it was passable. The rear sprocket though would need replacing, the teeth were heavily worn.... and it doesn't appear to be a part that's reproduced. Ah the joys of ancient vehicles!
Once again my little lathe saved me. I bought a modern reproduction sprocket from (...you guessed it) a C10 that happened to be the right tooth count for the right pitch chain, and used the lathe cut the teeth off as a ring. I then turned my original sprocket down till it was a nice fit inside the new ring of teeth and, once I'd added a nice big chamfer for weld penetration, clamped both parts to a nice big bit of steel box section and welded the two together.
One unobtainable sprocket problem solved. Excellent.
Now the front hub. This was not such good news. The braking surface looked bad, and once I'd started cleaning it up, it only looked worse. I did manage to mount it on my lathe, but it was really pushing the little lathe beyond it's limits and it soon became clear that if I turned it till the rust pits were gone then the hub would be perilously thin. It was looking like a job for a professional fix to get something safe enough I'd trust my life to it (not worth taking risks with a motorcycle front brake in my opinion!).
Now don't hate me... I was scratching my head about what to do when I saw the brake I'd recently removed from my 70s Suzuki looking at my from under the bench. It's a full width 8" twin leading shoe drum from a Honda CB77. It would be a serious upgrade over the original half width 5.5" single leading shoe BSA brake.
As I had it to hand it seemed silly to overlook this free safety and performance upgrade option. I have saved the original hub, should I ever decide that originality is important, and made sure to fit the Honda hub in a way that dint require modifying any of the BSA bits should I wan't to put it back at a later date.
So great, I bought a new 19" wm2 rim and spokes to suit the Honda front hub, and repurposed the old front rim, building it onto the rear hub.
The lathe once again came into it's own here, allowing me to make a new axel with the correct metric diameter to fit in the Honda hub bearings with custom spacers, imperial threads and custom sleeve nuts to suit the BSA forks.
Ok, no we're getting somewhere. Time to have the big kids mechano day and start bolting some bits together till we have something that looks like a bike! Was wonderful to see it looking like a bike again rather than just a pile for parts, as it had for the previous year.
Still a long way to go though...
As mentioned on page 1 of this thread, I'd already had the gearbox to bits once, but now had sourced a NOS kickstart pinion gear, here you can see new Vs old.
That was soon installed in the gearbox, and after it was mentioned earlier in this thread that the end float was critical (and also thankfully about the left hand threads!) I did some re-measuring. I reduced the gasket thickness to get the end float of the shafts back into spec.
I cleaned up the clutch, the clutch friction discs were pretty oil soaked, but I felt they cleaned up ok and the clutch seemed ok when I originally got the bike so I presumed would be ok now (foreshadowing... it wasn't!)
The clutch was now assembled, and installed along with a new primary chain and drive chain. I also turned up a chain guard mount / crank case breather / chain oiler from a bit of brass hex, to fit into that threaded boss I repaired on the engine cases.
Whilst on the subject of chains, now seemed as good a time as any to install the magneto and it's drive chain. The mag was making a pretty small spark when spun by hand on the bench, but it was a spark none the less and I'd seen the bike running on this magneto so decided it would be ok for now (foreshadowing... I don't think it is!). I used my dial gauge and got the mag timed to full advance at 1/2" BTDC as specified I the manual.
Handle bars next. This bike uses a very unusual 'split' handle bar, almost like a clip on works on a modern sports bike, there are two separate bars, one for left and one for right.
The bars that came with the bike were bent, and I think possible even not a pair. I did try to bent them into line, but I just couldn't get them to be symmetrical! Of course they are damn near impossible to find secondhand and no one makes reproductions, so time to improvise again. I bought a cheap set of reproduction BSA bars from a B31, cut the middle out of them and made up some solid plugs on the lathe which I welded into them to make a new pair of split bars.
Now I could start running all the control cables. A couple of universal cable kits helped here, and I soldered various ends onto the cables and made it all work with the mis match of parts I had. The only cable I didn't make was the front brake (did I mention not taking chances with brakes!), thankfully I could just use the Honda cable and Suzuki lever.
The fuel tank was fairly grim inside, so that got a POR15 lining. As a poster on this thread pointed out, it's the wrong tank for the year, and should be nickel plated with darker green inlays in the side. I'd like to at least paint it to look correct for 1934, but a job for another day as spring was well on it's way and the road was calling!
I cleaned and rebuilt the carb with new jets and needle, and bought a secondhand choke mechanism to replace the missing one. Next on the list was to solder up some copper fuel and oil lines.
The original front mudguard was truly beyond repair, being twisted and bent and rusted and having been previously bodged several times. I had to cut the hacked up mounting off the forks and turn up a new piece, which was in turn welded back on to the forks and I mounted a smaller more 'racing' inspired front mudguard.
And now we're really getting somewhere. Bolt on the rear mudguard and the seat, and we've got something that is ready for a first start attempt.
Well from the first kick I could feel something was wrong and it was quickly apparent that the clutch was slipping. On a 'pre unit' bike like this, with separate gearbox and engine, the kick is usually attached to the gearbox and relies upon the clutch and then primary chain to transmit it's force to the engine. So most of my effort was just going int slipping the clutch hand the engine wasn't turning over fast enough.
So I stripped the clutch and checked it all appeared to be together right, cleaning it again and had another go. No better. I went through a few rounds of this before deciding to 'rough up' the steel plates a little to give them half a chance of gripping the old friction material. And with that...
https://www.youtube.com/watch?v=SaHiZLQ2hT4 (https://www.youtube.com/watch?v=SaHiZLQ2hT4)
Excellent, and very straight forward. A quick run up the access road behind the house showed some immediate issues though. A few small easily fixed ones, the rear brake rod needed adjusting to put the pedal where I wanted it, bits like that, but 2 big issues. 1. I couldn't get 3rd gear and 2. the oil pump didn't appear to be working. The gear selection turned out to be an easy fix, in all my messing about with the clutch I'd managed to set it up so that the clutch arm now fouled the gear selector and locked me out of 3rd when the clutch was pulled. The oil pump worried me more!
I had pre-primed the bike with oil, as the user manual suggests, and so no harm done. Thankfully the antiquated total loss oiling actually helped me here. Would have wiped the bearings out of a modern engine running it with no oil pump for even a few seconds!
Anyway, looking in the sight glass I had no oil pumping. The pump came apart easily enough, and it was clear that small bits of corrosion from inside the fuel tank had gone through the pump and jammed in some of the tight internal tolerances. With a good clean out and a bit of light sanding to remove some burrs it looked like it would work again.
And it did, I now had a regular 'drip' in the sight glass, excellent. I had ot guess at the amount of oil needed, and massively over estimated to start with!
So feeling like the bike was essentially ready to be ridden I had one last challenge to deal with, electrics. I'd considered just removing the lights and running in a daytime trim but I did want a brake light. I would be going out on 21st century roads and people expect you to have a brake light!
I considered running just a small battery to power a brake light, but then I figured as I did have the charging system on the magneto and from running the bike I confirmed it put out some voltage, so making use of that made sense really. The break through came when I went to buy an LED bulb for the brake light, I did the calculations and realised that LEDs draw so little power that I could fit full modern brightness headlight, tail and brake lights into the original (well reproduction...) light units that came with the bike and still be drawing less than 18w. I also found a tiny little 6v house alarm battery that I could tuck up underneath the fuel tank. A cheap cycle speedo completes the electrics needed.
I've got to say that the headlight impressed me, it's better than my 70s Suzuki for sure, I shall have put an LED bulb in there too I think! And even better, I can confirm with the ammeter than the draw with all the lights on is less than the charging system can put out, so that's good news.
Test ride time, for real, out on the open road... Only once again the clutch is slipping, and slipping worse than ever now. Stripping it down, I'm pretty sure the issue is the old friction material is just shot and seems to leave a greasy residue even though I gave it a thorough cleaning with clutch cleaner. New clutch material is tricky to come by, I found a couple of corners of the internet which said I could order some ,but it was from small stranger websites I'd not heard of before on the other side of the world.
Ultimately I just needed two rings of clutch friction material, so I started looking for other applications that might need a similar thing. I got close when I found various tractor PTOs use similar friction rings, but I didn't find any quite the right dimension. Then in a stroke of pure luck, I came across the fact that the classic Fiat 500 uses a clutch disc of the same size, and even better I own a classic Fiat 500 and have a spare clutch in the shed! Comparing the two they were a perfect match. All I had to do was drill the rivets out to take the friction rings off the centre hub and there would be the parts I needed. Pic to show BSA clutch friction resting on top of Fiat clutch disc for matching size.
It turned out, the spare clutch I had in the shed was probably just as worn and oil soaked as my BSA bits were though (also as asbestosy I'm sure!!), but thankfully Fiat bits are cheap and easy to come by, so I had a new Fiat clutch some next day for £28. Frustratingly this was just 1-2mm larger diameter than my old 1960s Fiat clutch, and whilst in the Fiat this didn't matter, in the BSA this was a problem.
Happily I own a lathe and so, with confidence that the brand new clutch was not asbestos, I quickly popped it on the lathe and turned it down to size. Wit the rivets drilled out I could drop the new friction material into the BSA and cross my fingers.
First kick didn't inspire me with confidence, but I'm pleased to say its just got better and better as it's bed in and I'm now happy to draw a line under this and say the clutch issue is sorted.
Now I could finally go for a ride! All geared up and ready to see what this bike is all about, I made it a whole mile up the road before I noticed the oil pump wasn't pumping again, had a panic and limped back home. It turned out to just be an air bubble in the oil line and nothing to worry about, it had sorted itself by the time I got home.
That mile up the road was enough of a ride to show me several more issues to fix. Several easy adjustments to make, such as tightening up the advance and choke levers, as otherwise every time I hit a bump the choke went on a bit and the ignition retarded a bit!
I also made a new mounting bracket for the front of the seat, that raised the front edge and moved it back a couple of inches. I've seen a wide range of seat mounts when looking for into on these bikes, and given that mine is a bit of a mix and match special, I'm not surprised that the seta and bracket combo it came with wasn't right. Anyway, with the new briquet the riding position was hugely improved.
I also made a quick heat shield for the exhaust, as it was already trying to burn a hole in my leathers!
Ok, try again for a ride! This time I made it about 3 miles, before it started spitting and running worse and worse, kicking out clouds of smoke. I turned for home and tried in vain to make it back, but ultimately was forced to push it home the last couple of miles. After a bit of head scratching I realised that the nipple had come off the choke cable (this is why I didn't trust home made brake cables! haha) and the choke had come back on full, and secondly that the oil pump was adjusted wrong and had filled the bottom of the crank case with far too much oil, which was now being forced past the rings and fouling the plug.
With that sorted I was finally able to take it on a few short local rides which didn't involve break down or pushing home.
https://www.youtube.com/watch?v=DRn7pkbv_og (https://www.youtube.com/watch?v=DRn7pkbv_og)
I'm still working through the teething issues though, and am confident that bike's not running 'right' yet. I knew it would be slow, but currently I'm topped out at around 40mph on the flat most of the time (had it up to 51mph on a downhill with my head on the tank!!!) and at that point I can feel the engine missing and surging with the odd backfire.
I've tried playing with jetting, and having manual control of things like ignition advance and choke does make trouble shooting some tuning issues easier but I'm getting nowhere really. The best results I had were from reducing the plug gap... which leads me to think it might be a magneto issue.
Many magneto issues show up as poor starting, something I'm not suffering with, but it still seems like my mostly likely culprit. So when I've next got some time to tinker in the shed I think I'm going to have to get the magneto apart and see what I can see!
Magnetos are a crazy world of black magic and secrets, or so half the internet would lead me to believe! But if it's already suspect, I figure it's worth me investigating at home before I pay for someone to fix it right!
Thanks for posting your updates. As a B2 owner myself, I really appreciate you posting all this as it shows what is possible and the ways you've found a way round the issues you've faced.
I think I mentioned earlier in the thread that I considered getting your bike when Andy Tiernan had it for sale, but decided against it. I'm pleased I didn't get it, but by the same token also pleased that you did, and that you're posting progress as it's really interesting to see. Knowing what it was like beforehand, I wouldn't worry about originality too much; so long as it's on the road and being ridden that's the main thing.
Good to hear of your success. Really nice tickover. If it's backfiring when pulling, this is lightly to be to do with the Maglita. Lucas suggested 0.010" to 0.012" for the points gap.
One of the things to watch out for is the minute spring in the centrifugal cutout. These are made of non magnetic Berrylium, and easily fly off when dismantling. I have a number of them currently orbiting Saturn.
Bearing Part nos. are KLNJ 5/8 and KLNJ 1/2. I would test the length of spark on a spark gap tester.
Regarding your clutch, Saftek at Cleckheaton can make new discs, which are 125 x 90 x 2.4 if you need new ones. I often use a thinner or thicker one behind the clutch drum, to correct chain alignment.
BSA did 2 clutch drums. One had open slots for the steel discs (which let in oil), and the other was closed.
I find it's important to close the oil tap when the bike is not in use, otherwise oil runs into the crankcase and when you start the engine, it blows the oil out of the breather, soaking the clutch. I also find it's important to remember to turn the tap 'on' before starting the engine.
Adjust the oil pump to give a trace of smoke when opening the throttle after a short downhill run, otherwise you will be overoiling and your clutch will start to slip.
Hope this helps.
Well I'm glad it's helped you know you made the right choice Courtney! Thankfully I knew what I was getting myself into, when a dealer says 'it needs a bit of tinkering' you know it's bad. haha.
As a fellow b2 owner, what kind of performance do you think I should expect when it's running right? Do I have unrealistic expectations of mine? I was assuming it would sit at 50ish on the flat and do 55-60 with my head on the tank with a tail wind?
Thanks for the tips Steve. I have fitted an oil tap to my bike, but when it came to me there wasn't one fitted and the clutch was definitely oily!
There is some strangeness around the clutch material sizing. I did order some clutch material from Draganfly, based the part numbers from the 1934 parts book before I dug too deep into it, which was indeed the 125x90mm that you specify, but when I came to fit it, it was much too small. My clutch was ~155x130mm. I found a reference on Cornucopia (I think... or could have been some other small website) for B2 clutch friction material at 155mm OD, but not stock.
I've now had the Maglita essentially completely to bits, though I didn't fully remove the armature from the main body as there's lots of chatter online about 'keepers' and it loosing magnetism by doing that. I gather it applies to some magnetos and not to others, but I was able to see what I thought I needed without removing it, so I didn't risk it!
What I did find was a lot of general dirt build up inside, some of which being metal filings etc, so presume that doesn't help. I also found the that the coil winding wires had been both crimped then soldered to the ring terminals where they attach to the ground/points. One of them I think had a fractured solder joint, so have re-soldered that. The resistances of the coil check out ok.
I tested a theory I found online about using some largish neodymium magnets as a simple way to re-magnetise old magnets, I'm unsure if it did much, but I think it did help a little. The armature seems to 'snap' into discreet positions a little more positively than before.
Point are set at 0.010", maybe I should try 0.012" if I'm running short on other ideas! As far as I can tell, my Maglita is not fitted with a cut out? Unless it's inside the armature itself?
When I next get chance I shall put it back together and see if theres any improvement!
On looking at your photo, it's not a B2 clutch. Perhaps of Oriental manufacture, or maybe Fiat?
I seem to remember Lucas recommended a plug gap of 0.015".
Yes, mechanical cutout is in the end of the armature. If you undo the "disc" nut with a peg spanner, remove the end plate and bearing, the cutout is beneath the tufnol and copper discs. Careful with the spring.
I have never known these cutouts to give any trouble.
I just use a couple of spanners either side as keepers. Seems to work OK.
I think your expectations of performance are a little high. In my experience, a Blue Star Junior will do 50mph, perhaps 60 if you don't mind it blowing up, but they do go very well for such a small 90 year old engine.
I would think 45mph, maybe 50 for short bursts, and if it will do that, you have a very good engine. But let's see? I wonder what others think?
Regarding LED headlights, I find they singe your eyebrows when looking at them, but, out on the road, they are quite useless with no concentrated beam at all. All they do is vaguely light up the surrounding country side. This with a new reflector and adjustable focus.
The photo there was of the Fiat clutch against the BSA friction discs just to show how similar they were.
I've attached a couple of photos of my clutch assembly here. It certainly looks 'right', so I presume it might just be a clutch assembly from a slightly different year BSA?
That's fair enough if I was being a bit optimistic about performance! Either way, I wouldn't expect it to be surging / back firing when ridden at speed os will keep chasing issues. :)
There's no disc nut on the end of my magneto armature? Just a normal hex head, which when removed allows me to remove the points cam which is keyed to the magneto shaft. Also yes, that's a modern condenser in there, as it's externally mounted it was a quick easy thing to try swapping out incase that was the root of my weak spark, but sadly made no difference.
I was always dubious of LED lights, but I have to say the latest crop have really improved. I've used www.classiccarleds.co.uk a couple of times now and been impressed. Ultimately my headlight is now as bright as if I'd fitted a 60w Halogen bulb, and yet it draws so little power that the limited output from the Maglita has no problem keeping up.
My apologies. Please ignore my comments about your clutch, which is the correct and original clutch. Apart from being a bit thick, the confusion arose because I'm using the Blue star single spring clutch, which is quite different. And I forgot it's me that's using the wrong clutch. Also, the car centre plate confused me, but of course that's the Fiat plate you removed the friction discs from. Sorry about that.
Unfortunately, I can't post pictures. It just says the file is too big and I have no idea how to make them smaller.
Re the headlight, have you been out at night? Which bulb are you using?
I'm using 35 degrees advance, which I find very satisfactory, but I don't know the distance measurement.
haha, not to worry. I could have worded it better and included more pictures to demonstrate how I was making use of the Fiat clutch parts.
Yes I've been out at night and I was quite content with the brightness. As I said, better than my 1970's Suzuki headlight!
I'm using this bulb, with was a direct fit into my reproduction headlight bowl; https://www.classiccarleds.co.uk/products/bpf-p36d-437-368-370-414-led-headlight-upgrade-6-12-and-24-volt-negative-or-positive-earth-great-beam-strength-and-pattern?_pos=1&_sid=9c1304850&_ss=r&variant=39564853379181
I went for the 3000K colour, warmer and softer than some LEDs, but it still isn't quite as warm as a tungsten bulb.
I'm set to the 1/2" of advance specified in the manual, with a plug gap of 0.023" . NowI'm sure I read that somewhere, but I can't for the life of my find where I'd read that as correct! Checking the manual I can see 0.018" listed. So maybe having too large a plug gap isn't helping me.
The bike is back together now, so I'll hopefully get out in the next couple of evenings for some test runs and will report back.
Thanks for the LED info. I'll try one.
I 'm sure that 0.023" is too large a gap. It must be a very good Maglita if it starts on that. However, it may be the cause of your problems at higher speeds.
Have you discovered the Advance/Retard Stop? May be worth playing around with?
Just come across your thread.
Really interesting and well done for overcoming all the issues so far!
Thanks for taking the time to post.
Hope you get the misfire sorted before we run out of summer!
Thanks Stubaker58. :)
First test ride report; better but not fixed. I've picked up some speed, was hitting ~45mph on the flat, but when heading for high revs its still missing and popping at times.
The bike runs the same with 0.023", 0.018" and 0.015" plug gaps. So I've left it on 0.018" for now.
Back to the drawing board! I think the magneto overhaul has made an improvement, so I'll have another pass through the carb jetting options. The weak spark could have been giving me a false sense of which jets worked best.
The carb is back to standard wit thew needle in the 4th position and the 75 main jet, but obviously fuel is very different now to that from 90 years ago when the bike was made.
If the carb improvements don't help, my next thought is whether the valves are floating due to weak valve springs. It is only right at the top of the rev range the the bike misses. This thought was triggered by reading some other threads on here.
I did fit some NOS outer valve springs when I overhauled the head, as the ones that came on the bike were clearly soft and deformed with age, but I couldn't find any inners. I make take some measurements and see if I can find a modern alternative spring.
Steve is right about performance/speed. Mine will do 45-50mph at a push (that's if my speedo is right), but it's happiest cruising around 30-35mph on back roads. Mine had a fair bit done to it before I got it - re-sleeved, new piston etc., so I think my engine is pretty decent and the magneto was overhauled and recently remagnetised. Nothing has been done with the gearbox as far as I know, but one thing I do need to sort out is the oil pump as the worm is worn. I'm running an old KLG spark plug that's probably as old as the bike, and it works far better than any of the modern replacements I have tried, so I would definitely recommend hunting around for an old Lodge or KLG as the bike will start and run better.
Very late update, but I thought it might be of interest to know that after many unsuccessful attempts to fix the misfire I have finally found and fixed the issue.
It appears the spring on the points had gone soft and was allowing the points to 'float' at higher engine speeds, thus loosing spark and causing the misfire. After a bit of a bend to the spring to give it a bit more tension again, the engine finally feels like it's running 'right', which is a huge relief.
It's not really that much faster mind! But it's good to have found and solved a problem.