I'm having some difficulties with my primary chaincase. The inner chaincase was pretty bashed and has had a rough hole cut in it where the sliding gearbox shaft plate should be. In fact, it was so stretched and deformed that I had to cut slits with a grinder and then weld while clamped to a flat surface. This has largely worked, although there's still some "oil-canning" toward the where the case is fixed to the engine.
My problem is that there seems to be very little clearance between the clutch and the rear drive-chain/sprocket and getting the chaincase into a position where neither the clutch nor the chain is rubbing is driving me mad. I wonder if this is due to the omission of the sliding gearbox shaft plate. Any thoughts/experience welcomed.
David
Just an addendum: I should have asked if the omission of the slider could be the issue and whether anyone knows if the slider from the later B/C/M models might fit - Draganfly make them for a very reasonable 25 quid.
OK, I've now got to the bottom of this and there's a salutary general lesson for all buying an unfished restoration project.
As you can see from the attached, when I bought my machine it looked pretty tidy (apart from truncated front guard) and had had a lot of important work carried out - reconditioned carb, mag, wheels rebuilt (shame not chrome rims), powder coated frame etc. The vendor was perfectly honest with me and said that the engine had been rebored and the head sorted but that the engine had been rebuilt by a couple of friends as had the gearbox. Unfortunately, these friends were not very bright as I will come to. I stripped the engine as a matter of course and found the crank wanted extensive work which set me back over a grand - that's OK, almost what I expected.
As I've gone through the machine I've found that just about everything has been very badly "rebuilt". The wheel bearings were completely knackered, the forks were dangerously worn, the mudguards were shockingly poor especially the rear which even had the wrong stay. Even the brand new rear chain was completly the wrong size. However, the gearbox seemed OK, that is until it came to fitting the primary chaincase.
I now realise that whoever rebuilt the gearbox decided to make their own gaskets from thick neoprene or similar and that the input shaft is consequently in the wrong position which not only makes the clutch sit too close to the output sprocket but also means that third gear doesn't fully engage. Hopefully the bearings will be OK and I can just make up some paper gaskets to set things right. As you can see from the photo, pushing the input shaft out to the correct position moves everything 2.2mm which makes a world of difference regarding clearance for the primary chaincase and also gives the correct engagement for third gear.
And the lesson is... all that glitters is not gold!
David
PS I'd still be interested to know if anyone thinks the slider from later models will fit and be of any benefit.
PPS I should add that I only paid £5K for the machine, so while it turned out to be less of a bargain than I'd hoped for, it's not such a bad deal and was certainly worth the punt of buying on the strength of the photos and a couple of conversations with the genuinely honest vendor.
That looks really nice. Full marks for sticking with it.
Thanks, the beauty in those photos is only skin deep, but I'm turning it around into a mechanically and aesthetically sound machine!
I have been through the gearbox saga and no gaskets are shown in the parts book until 1937. Also in 1937 shims were listed for the mainshaft. Not for the layshaft though.
Interesting. I'd not spotted the lack of gaskets in the parts book. Mind you, there are quite a few parts I can't find such as the stud that secures the outer primary chaincase cover to crankcase.
I'm inclined to fit gaskets and also shim as necessary. I've done a lot of geaboxes in my time - the performance of a Moto Guzzi gearbox is particularly dependent on careful endfloat shimming.
Any thoughts on that slider plate btw? Looking at the parts books I have ('32 and '34) it doesn't appear to be shown. There are two holes in my chaincase which look like they're to hold it and Only British Austria have new chaincases which have the slider plate fitted.
I have 2 hand change boxes, one with gaskets and one without. The one with is in the bike , no modifications to swimming and works fine. The one without is a rebuilt spare with new bushes etc and the end float on both shafts is perfect. I don't think that this is as critical as modern bikes.
With regard to the sliding plate, it is missing on mine also. The later ones are dimensions similar but the flanged part in the middle is too deep. Without the plate, oil leakage is next to nothing. The main problem is that there is no seal on the outer case. The chain is lubricated from a breather pipe from one of the chaincase studs. This is adjustable from the screw and locknut on the crankcase. Once oil fills the chain dip on the inner case the oil leaks, especially on the side stand.
It is worth fitting a sealed type high gear bearing. Also I modified the kick-start shaft to take a thin o ring. The gearbox oil level is up to the mainshaft and theses mods stopped the oil running out both ends.
Thanks. I think I can live without the slider plate. I modified my '32 Sunbeam 9 gearbox to take neoprene seals - worked a treat. The primary chaincase is like a Swiss cheese, so oil loss is an inevitablity. Given the very low mileage this machine will do, I'm inclined to close the oil-feed down to a minimum.
The adjuster backed off from tight is sufficient to lubricate the chain without the bike embarrassing itself too much when parked.
Thanks for the tip.
I have two pre-war BSA Vee twins and both have the slider on the inner chaincase. The only contribution I can make is to advise using Thixotropic grease "Century EPLITH 00" in the gearbox. This grease becomes an oil under pressure between the meshing gears and provides excellent lubrication without leaking out of the gearbox which has no oil seals. I have been using this grease for over 50 years on several pre-war BSA;s with no problems at all. Hope this helps.
Thanks Alan. How does the grease lubricate plain bushes? It obviously does otherwise you wouldn't be using it for all this time!
BTW & FYI, Mark Quinney tells me that the inner gearbox gasket is the same as that fitted to M20/21 models. I've used ThreeBond 1184 Liquid Gasket which I can recommend for sealing crankcases etc. It's not silicone and better than old fashioned products like Hylomar (good in some circumstances) or Welseal (also has its advantages).
Hi David, on the rare occasions I have dismantled my vintage BSA gearboxes there has been plenty of lubrication to all spindles and bushes and I have never detected any wear in the bushes. As it is not possible to see inside the gearbox when the bikes is running I can only assume that the liquid grease finds it's way to the bushes. Thixotropic grease was recommended to me when I first started vintage motorcycling and I have given quite a lot to VMCC friends. 50 years ago I could only buy it in large drum and it will outlast me as topping up is needed very seldom.
Many thanks Alan. I found some EP90 in the shed so I'll use that for now (though I note the manual says engine oil), but I'll order up some of the thixotropic grease, it sounds like an excellent solution and one I'm sure BSA would have adopted if it had been available at the time.
I'm going to use 20/50 multigrade in the engine as I've never seen any good evidence to show that straight oils are preferable. Again, I think if it had been available in the 30s BSA would have used it. I note that for the 54-61 B-series machines the Haynes manual recommends 20/50.
Hi David, DO NOT USE EP90 in your gearbox. EP90 contains additives that dissolve phosphor bronze & brass bushes. If you want to use the bike before you can source some Thixotropic grease use a straight 50 grade mineral oil although it will leak out. I run all my vintage BSA's on straight 40 & 50 mineral oil which are readily available. Regards Alan
Thanks for the warning Alan, but I think you're thinking of what has sometimes been said of Molybdenum Disulphide. I seem to remember a friend saying something about brass caged bearings, but corroding when he used MD grease. However, there's little evidence suggesting incompatibility between MD, bronze (copper tin alloy) and even brass (copper zinc alloy).
EP90 on the other hand is specifically formulated for gearboxes containing bronze bearings and I can find no mention of incompatibility with brass. I think I've used EP90 in every classic gearbox I've ever reconditioned and done thousands of unporoblematic miles.
Hi, it is up to you what you use. However, I also have, rebuilt from a wreck, A BSA 4 seater 1938 Scout (car). It is well known from bitter experience in the BSA Front Wheel Drive Club that EP 90 dissolves the bronze casting of the front wheel system. It doesn't happen overnight but after only a few years all the teeth on the bronze casting are eroded away due to chemical reaction.
Anyway it's up to you. I wish you every success. Regards Alan.
Many different opinions. Here's mine.
I don't understand how you can move the mainshaft out to the "correct" position. The splined register on the mainshaft sits against the sleeve gear and the mainshaft cannot move further outwards. (Earlier gearboxes had a thrust washer here). The distance between the gearbox sprocket and the clutch sprocket is set, and cannot be altered except by machining, or perhaps a badly worn taper, or maybe you have the wrong clutch hub?
You must use a sealed main bearing. Use an LLU bearing, which is a contact sealed bearing, not a LLU bearing. Then you can use 50 grade oil as recommended, without leaks. Don't forget the felt washer on the clutch pushrod before you fit the outer cover.
It seems using a sliding plate will make your clearance problems worse. ( Not fitted on 1934 Blue Star).
I think you should firstly check sprocket alignments and work from there.
The Blue Star gearbox is essentially the same as the early M20 gearbox, (later ones had a completely different outer cover for enclosed footchange) and you must set mainshaft, layshaft and selector shaft endfloat for a good gearchange. Do not tighten the kickstart ratchet nut more than finger tight.
The inner cover gasket plays a part in setting endfloat, so I would not use silicone sealants etc.
There are many washers and spacers on the mainshaft, some of which are not shown on the M20 diagram.
I have read of people using Thixotropic grease for many thousands of miles without problems and I have also read of gearboxes seizing up solid within 50 miles. I don't know how quickly (or if) the grease becomes liquid, but it has to move through 1/8" holes to lubricate the bushes. I have found it's not that difficult to make these gearboxes reasonably oil tight.
My understanding is that back in the 50's EP oils attacked bronze, but they quickly resolved the problem.
Finally, I too had the problem of a warped inner case not clearing the sprockets, so I fitted it and used a stout screwdriver to lever it about until it cleared.
Hope some of this might help.
The mainshaft should have the distance washer (24-4237) between the timing side bearing and first gear Steve. Without this the shaft is free to float and there's also nothing to secure first and second gears to the mainshaft spline.
You mention only doing up the ratchet gear nut finger tight, if the distance piece is missing this is the only way the mainshaft could rotatate since first gear will bind against the inner cover. In fact without the distance piece the mainshaft will float back and forth with only fourth gear checking movement at the clutch side and the casing on the timing side - not good as it will slowly grind away the casing over time. The distance piece allows the mainshaft to be clamped to the timing side bearing and puts the clutch in the right place relative to the gearbox sprocket thus giving sufficient clearance. I've made and fitted this part now and all is well.
As you say Steve, the slider plate may well have made things worse, but at the time my thought was that the gearbox had been properly rebuilt and that the problem lay with a warped chaincase as you mention.
As this is what BSA specified, I'll use some engine oil until I get the grease you mention Alan, but not because I think the EP90 will harm the bronze. As Steve says, maybe there was a problem with EP90 in the early days. Oil refiners spend millions developing and testing products and they won't risk being sued over a false compatibility claim and they all say that classic EP90 and other hypoid gear oils are bronze compatible.
Anecdotes should never be confused with actual evidence. I can provide the following anecdote to prove this! My father rebuilt a car engine and rather than using his usual Castrol GTX, filled it with Duckhams oil. The engine siezed and my father insisted it was due to the oil (in fact he always replaced the D of Duckhams with an F following this incident). Is it likely that an oil made by a massive multinational to an exacting specification caused the issue? Of course not, probably an oil gallery was blocked by some gasket cement or similar - in other words, operator error.
With all that said, following Alan's experience, I wouldn't take the chance of using EP90 if I owned a BSA Scout!
So that's how you got the mainshaft to move outwards! There is also an oil flinger washer 24-4235 which sits between the distance washer and the gear cluster.. I found a distance washer that was 0.128" thick, and a Draganfly replacement was 0.118" thick. Selective assembly? The cluster should be an interference fit on the mainshaft, and will need a sturdy press to remove.
I had not mentioned the distance piece in my last post, but of course you must not assemble the gearbox without it. It would be disastrous, as you suggest, and give about 1/4" of mainshaft endfloat.
It is BSA who say that the ratchet nut should only be tightened finger tight. It is locked in place by the tab washer and locknut. Search for the M20 instruction manual.
If you've fitted a sealed main bearing, then I'm pretty sure the gearbox won't leak with 50 grade oil (mine didn't leak), but the choice is yours.
Now then, should you fit a sealed bearing to the inner cover? I haven't because I don't want the kickstart to run dry.
I absolutely agree with you about GTX and Duckhams.
118 thou sounds about right - I think mine came out at about 3mm, but as you say, I employed selective assembly and made one spacer of 2mm and a 1mm shim. I machined the spacer until I could measure a small amount of end-float, about 0.3mm.
I wonder why BSA specify finger tight for the ratchet nut? I doesn't really make sense since with the spacer in place the ratchet nut tightens against the ratchet bush and fixed gear, pulling the mainshaft assembly into place and locking it on the ballrace. I can't see why this wouldn't be desirable, but my M-series Haynes manual says the same so, I'll do as I'm told!
In the case of my 'box, first and second gear were only a little tighter than a transition fit and the mainshaft driven out with relatively little force.
I certainly agree about fitting an RS shielded main bearing, however, unfortunately, someone has fitted a steel shielded 2Z bearing and I can't be a*sed to change it. I like Alan's thixotropic grease idea anyway, so oil leaks shouldn't be an issue.
I too did what I was told.
I think you will find that the cluster gear should be a very tight fit on the mainshaft. If you ever strip the gearbox again, you might want to assemble it with some Loctite. I don't know how important this is, but if it moved in use, could it contact the casing or perhaps alter the endfloat?
This is probably not relevant to you now, but I found that with a steel shielded bearing, when stationary, oil continuously dripped out until it was almost empty. Mind you, I mistakenly fitted the 2 oil retaining washers 24-4225 the wrong way round, which probably didn't help. I believe the inner one should be fitted so that there is a gap between the washer and the outer race, so oil can enter the bearing, and the outer should be fitted so that the outer diameter of the washer just contacts the outer race, and so tends to provide a seal. I found that, in practice, although the washer turns against the stationary outer race, it only rubs very lightly, and just tends to polish the outer race.
Assuming the washers have been fitted the right way round, it might be worth filling the gearbox with oil, to 1/2" below the top of the filler neck, and see if the oil comes out through the bearing. Oil came out of mine straight away, so, as you say, thixotropic oil may stop the leaks. Do you have to heat it to pour it in? I know Douglas used this oil, but they fitted a grease nipple and I gather you just pumped away until it started oozing out all over the place.
Anyhow, good luck with it all, and let us know what it's like on the road.
Thanks for the reply Steve. In fact the first/second cluster can't go anywhere as the distance piece captures it between the end of the splines (3rd gear end) and the timing side bearing. Only if those finger tight nuts come loose can the shaft move, but even then, in my case, it can only float by 0.3mm.
I hate oil leaks. I modded the gearbox on my Sunbeam model 9 and the whole bike didn't drip a drop. Even the Triumph twins I've owned were completely oil-tight (only after rebuilding and careful assembly though). If it wasn't for the promise of thixotropic grease I'd pull the 'box to pieces again.
Where does the push-rod felt washer you mentioned fit?
I don't know if it was a typo, but the only nut that is finger tight is the stepped nut against the spring, followed by the lockwasher and then the locknut, which should be reefed up very tightly.
The felt seal 15-270 fits over the clutch pushrod between the ratchet assembly and the outer cover. On the first gearbox I did, I assumed this felt fitted on the outside, like the Sloper and was very small, but whatever I did, I couldn't get it to stay in place. Silly me.
If you look on the WDM20 forum, in the technical section, you will find a very useful list of all the washers, felts etc. entitled 'Gearbox Identification'.
By the way, I also reduced length of the kickstart bush by about 1/8" (3.2mm in foreign currency) and fitted an O ring and a thin shim washer between the casing and the kickstart. Seems to work.
Thanks Steve, I wonder if an o-ring would be better than a felt washer. I shall investigate.
David, Regarding your reply on 28th August, you might be interested to read Factory Service Sheet P051 dated February 1936 which is available on the Owners Club Library page.
Steve.
Thanks Steve. I'll double check this.
David