I didn't mean to buy this but at auction at Stafford recently it came home in my van. I'm new to BSA's but not at all new to building bikes. I intend to check it over and run it as is, have got the top end off and discovered it has been running methanol for a start which I'd like to continue. I will need help and have questions but first does anyone recognize it and have any history for it? It may have belonged to Martin Lampkin recently but the auction catalog was not clear on that, it's a '49 frame (that should be plunger) and a '53 engine, gearbox has no marking. Last run at the 2007 Thunder sprint? Thanks, Joe.
Looks great... You do realise that Methanol requires the carb jets to be almost 3 times larger than Petrol. For a 250 they would go up from 140 to 400 size, and the needle and tube would be different as well. The Compression Ratio could have been maxed out as well, so don't be tempted to run it on petrol. Also check what oil it is using, it could be Castrol R or Millers CB40 castor oil for these methanol engines. The cam could have been changed for a sprint cam, if that was what it was used for.
Hope you can run and bump it, or maybe you have the starting rollers.... Best of luck, hope you take it to a few events.
Quote from: scifi on 05 Nov, 2024, 21:59 Looks great... You do realise that Methanol requires the carb jets to be almost 3 times larger than Petrol. For a 250 they would go up from 140 to 400 size, and the needle and tube would be different as well. The Compression Ratio could have been maxed out as well, so don't be tempted to run it on petrol. Also check what oil it is using, it could be Castrol R or Millers CB40 castor oil for these methanol engines. The cam could have been changed for a sprint cam, if that was what it was used for.
Hope you can run and bump it, or maybe you have the starting rollers.... Best of luck, hope you take it to a few events.
Thanks, very happy with it so far. The main jet is a 900 and needle to suit. It has the 13:1 piston, exhaust cam is a common one but the inlet is just marked 48 and has a measured lift of 0.355". I'm going to make some rollers that run off one wheel of my van just for added danger :D Pics to follow.
Pics
Well done on the purchase. Looks like a serious bit of kit.
The cams are later cams (65-2449in and 65-2450ex that you expect on DB onwards tourers or racers (I have the same cams on my 51 ZB34 top end). The piston is 13:1 so definitely for running dope (mine is only running 7.5:1).
Your carb appears to be a later GP type.
Correct for your year would be the ill thought of RN type of 1 3/16". The year earlier would have been a 1 5/32" TT but I guess the later cams, high comp piston, megaphone exhaust will have their own settings and requirements that someone will have found by experimentation and experience. I expected the main jet to be around 1000 (vs my 500 has a 10TT9 settings of 360 main jet, 106 needle jet, needle position 3, slide 7).
Sorry wanted to edit:
65-2448 inlet cam
I'll be a bit suspicious if it has run on Castrol R. Could be that old R has solidified, blocking oil passages. Wasn't a problem when you stripped the engine between races. Modern castor based like Morris C40 has inhibitors. Run my Manx for six years on C40 without taking engine apart. Molnar changed his recommendation for his Manxes from castor oil to synthetic oil a couple of years ago. Changing needs a complete strip and cleaning. When I changed from a JAP speedway bike to JAWA in 1970, I also changed from R to a multigrade oil. The JAWA only needed a complete tear down twice a year. With synthetic oil you don't new so much warm up time before riding.
The oil drained pretty clean considering the time it had been stood, it had wet sumped but no surprise there. Some corrosion on the steel fittings on the fuel system and a little white powder from the dope.
This is what I found lurking in the cylinder head, any ideas? Modified? Inlet has been polished and exhaust appears treated and over size maybe. Numbers are not clear, some battle scars that have been dressed back so I'll probably leave them. I'm thinking dope runs cooler so not like a two stroke looking for sharp points for detonation.
There are two inlet valves of that size:
65-1842 (1.6")
65-1611 (1.599")
The details will depend on stem diameter and collet type - sure you know two types of GS collet.
The exhaust looks to be a special.
65-1644 is 1.524"
65-1759 is 1.53"
65-1630 is 15547"
It will be interesting to see the condition of the stems, top surface and which collets were used.
Similarly the condition of the crank and flywheel tapers/rivets.
Looks like it should the first type of short rod BB 6 7/8" con rod to match that piston.
Really good write up on valves on the britbike forum .https://www.britbike.com/forums/ubbthreads.php/topics/929282/1
I stripped the clutch today for inspection. Does this look like a standard unit? The ring round the outside is something I've done before on diaphragm clutches but I guess it helps the basket here as well.
IMG_4956.jpg
The bearing was wobbly for sure but I guess with rollers this narrow that might be expected. Even so there is play of maybe 15 thou, not measured it yet but it will need looking at.
IMG_4965.jpg
Can anyone help ID the gearbox? I cannot find any marks anywhere, is it original to the '53 motor? I've looked for stamps in all the places the 'internet' says to look.
IMG_4966.jpg
IMG_4969.jpg
That's a later (and reputedly better) four spring clutch unit.
The gearbox is the same as my '51 ZB32.
Thanks, does the gearbox have a designation code for ID should I need to get spares?
Possibly, but I don't know it.
It's the same gearbox as on the equivalent B31/33 so finding the correct part from Drags (if they're not on "back order"!) should be simple enough.
You will need to strip the box and count the teeth on the cogs to see exactly what you have. Likely a close ratio cluster available for ZB Goldies up to '53 with that box.
You should get the BMS book 'The Gold Star Book'. Probably the most useful starting point.
As above the clutch is later 4- spring version similar to the Triumph one. Some hubs are plain, others are fitted with a thrust washer, you have to remove the basket to see behind it. Rollers are special size (not 1/4").
I have the Gold Star book on the way from the US, finding quite a few bike related things easier and cheaper and even quicker from the US rather than Europe here in the UK.
To save me getting lost down a wormhole does anyone know if there is a belt drive conversion that will fit if I decided to go that way?
Quote from: Wildebeest90210 on 05 Dec, 2024, 05:24 To save me getting lost down a wormhole does anyone know if there is a belt drive conversion that will fit if I decided to go that way?
Yes there is a Newby clutch/belt drive kit. The clutch I used on my raid bike is by NEB which comes in dry/belt type or wet/chain options, but because I want to retain option of a Pearson electric start, I went with chain type. Thus far all good.
The belt obviates need for crank shock absorber and leaky chaincase (my biggest bugbear!)
How does it obviate the need for the shock absorber?
Supposedly the belt absorbed the pulses of the engine. A friend of mine had a Newby belt conversion on his BSA Super Rocket but got me to fit a conventional set up as he thought the belt drive to harsh. Having ridden it I had to agree. If you have problems sealing the chaincase do as I do and use a Cork gasket.
"Supposedly" would be right. Toothed belts don't give, and if they did they'd be no good as timing belts.
I am not a particular advocate for belt drive systems but going on the feedback from quite a few people that have fitted them. The Newby kits do not have a shock absorber in either the clutch hub or on the crank. It was designed for racing but many are on the road now.
The belts on these are not as tight as cam belts (they are supposed to allow a 90 degree twist to be slack enough).
I'm happy with my set up thus far having been warned re: super accurate chain alignment for the Dural clutch sprocket.
Leaks also occur from the hub flinger behind the hub. My conversion has the Pearson sliding plate and dual lip seal (long term report in progress!). That also has SRM sprocket nut (with seal) and the mainshaft bearing has a seal plus the dedicated seal around the sprocket in the case.
My off-roader is totally stock in this area except for foam vs felt slider seal.
Quote from: neil1964 on 06 Dec, 2024, 09:11 (they are supposed to allow a 90 degree twist to be slack enough).
That's the quick and dirty rule of thumb for all toothed drive belts, but that "setting" doesn't introduce any shock absorbing effect.
If riders are happy then good enough, but the bike is left with no mechanism for smoothing the engine pulses, which may be important to some.
I have spare 13:1 +0.5mm piston in good condition if it is any use to you.
For use on dope?
Quote from: Derek996 on 06 Dec, 2024, 13:45 I have spare 13:1 +0.5mm piston in good condition if it is any use to you.
Yes it might be, I plan to run on dope and will very probably have a blow up so would be good to have it ready. I'll try to work out how to send you a direct message.
Just click on his name on the left of the panel and choose PM.
Quote from: Wildebeest90210 on 01 Dec, 2024, 16:27 I stripped the clutch today for inspection. Does this look like a standard unit? The ring round the outside is something I've done before on diaphragm clutches but I guess it helps the basket here as well.
IMG_4956.jpg
I machined up a split coller to fit around the hub adapter , the amount of thread for a puller is ridiculous and the pullers strip too soft , I then use a bearing puller to clamp around that then screw in the Teo extensions and then put the puller bar across that , wind it up and give it a wack .cheers
The bearing was wobbly for sure but I guess with rollers this narrow that might be expected. Even so there is play of maybe 15 thou, not measured it yet but it will need looking at.
IMG_4965.jpg
Can anyone help ID the gearbox? I cannot find any marks anywhere, is it original to the '53 motor? I've looked for stamps in all the places the 'internet' says to look.
IMG_4966.jpg
IMG_4969.jpg
Quote from: Bigsingle on 08 Dec, 2024, 18:50 Quote from: Wildebeest90210 on 01 Dec, 2024, 16:27 I stripped the clutch today for inspection. Does this look like a standard unit? The ring round the outside is something I've done before on diaphragm clutches but I guess it helps the basket here as well.
This clutch looks like mine an early 4 spring triumph, common upgrade parts are readily available, the clutch adapters come in two slight variations the part number with A on the end is slightly bigger in the taper and goes on a little further .I can dig up the number if you require . Cheers.
IMG_4956.jpg
I machined up a split coller to fit around the hub adapter , the amount of thread for a puller is ridiculous and the pullers strip too soft , I then use a bearing puller to clamp around that then screw in the Teo extensions and then put the puller bar across that , wind it up and give it a wack .cheers
The bearing was wobbly for sure but I guess with rollers this narrow that might be expected. Even so there is play of maybe 15 thou, not measured it yet but it will need looking at.
IMG_4965.jpg
Can anyone help ID the gearbox? I cannot find any marks anywhere, is it original to the '53 motor? I've looked for stamps in all the places the 'internet' says to look.
IMG_4966.jpg
IMG_4969.jpg
Hi there, your BSA was at the 2007 thundersprint. I was also there racing our 1956 Norton Dominator sidecar. I was the one hanging off the side. Here is a fuzzy photo taken from a youtube video showing your bike. Unfortunately I have mislaid my old programmes so cannot identify the rider.
Ian
Quote from: Wildebeest90210 on 06 Dec, 2024, 21:41 Quote from: Derek996 on 06 Dec, 2024, 13:45 I have spare 13:1 +0.5mm piston in good condition if it is any use to you.
Yes it might be, I plan to run on dope and will very probably have a blow up so would be good to have it ready. I'll try to work out how to send you a direct message.
I sent you a private message about the piston a week or so ago but since you haven't replied I guess you haven't found it. If you look at the very top of the page you will see a heading marked "My Messages". If you click on it you will see links to INBOX and SENT Items. You will find new messages in INBOX.
Thanks, Can't see a 'like' button here but any history much appreciated.