bsa b31

[paternoster]

Hello there,

   I have been drooling over pictures of classic bikes for years now and the other day I finally bought a bsa b31.

 Its a 1948 rigid frame b31 350cc. the bike is complete but it is a non runner and has been sitting outside for years with no sparkplug in it. i have been told that it is a b31 engine but has a b32 crank, does this sound feasable?
nothing is siezed up exept the carb slide. so i dont rekon it will need much work.
i was wondering if anyone could give me some advice please. i would like to know how to start the engine once i have repaired it. i know about the obvious kickstart but i was told that the timing advance lever on the handlebars has to be set correctly. so how do i know if i have the various levers in the correct place? i was also told that if the advance/retard lever is in the wrong place i might be catapaulted through the shed roof by a backfire, is this true?
i would also like to know if the bike is likely to withstand a 3 hr motorway journey every so often, not regularly, just every 2 weeks or so.
any help would be great.
thank you

[L.A.B.]

b31 engine but has a b32 crank, does this sound feasable?

I don't have access to the 1948 parts book but the 1949 parts book lists the same parts for both crank assemblies, so I would guess that there shouldn't be a problem.

i would like to know how to start the engine once i have repaired it.

Nigel (VintageBike) has given good advice previously  about this:http://www.vintagebike.co.uk/cgi-bin/yabb/YaBB.pl?board=10;action=display;num=1103702097

i was also told that if the advance/retard lever is in the wrong place i might be catapaulted through the shed roof by a backfire, is this true?

It is possible to get a kick-back if the right starting technique isn't used but a B31 is unlikely to launch anyone into orbit!

i would also like to know if the bike is likely to withstand a 3 hr motorway journey every so often,

Yes it would but not at motorway speeds!
A realistic cruising speed of 50-60mph is about all you should expect, also taking into account the lights and brakes aren't up to modern standards so it may be better to choose another route?

it is a non runner and has been sitting outside for years with no sparkplug in it.

so i dont rekon it will need much work.

I wish I shared your optimism!

 

[L.A.B.]

i was also wondering if theres anything that can be done to the engine to increase that cruising speed a bit.

I'm not sure trying to increase the power output would be a good idea but you could alter the gearing to give a slightly higher cruising speed but you may lose some acceleration.

is there any modern alternatives for the brakes and headlights also, I have heard about this 12 volt converting teqnique, is it easy or massively difficult?

It is possible to upgrade the electrical system, A O Services should be able to give you advice.
http://www.aoservices.co.uk/
You could have the brake shoes relined with a modern lining material but I am not sure if there would be much improvement, or fit different brakes, but you may find the original brakes adequate?

[L.A.B.]

Unfortunately the parts book I have only refers to the plug by its part number, and the earliest handbook I have for this model only dates back to 1955.
The recommendation then was for a Champion L7, the modern equivalent to that is a Champion L82C or NGK B6HS gapped to 18-20thou (0.45-0.50mm).
I think it would be a good idea to consult a BSA specialist, as you are likely to need some other parts and a manual.
http://pages.eidosnet.co.uk/~canddautos/
http://www.draganfly.co.uk/  

[L.A.B.]

Good to hear you got it going!
The clouds of smoke were to be expected as it has been standing and likely that the oil had drained down to the sump.
Was there any oil in the oil tank?
Sounds as if you have a clutch problem of some sort?
Was it easy to select neutral after stopping the engine?

and it wouldnt switch off.

The bike should have a magneto that works independantly from the electrical system, some bikes have a kill button, but the handbook doesn't mention one, only to stop the engine using the decompressor lever (exhaust valve lifter).  

[L.A.B.]

As you say, will need to strip and clean all the clutch parts and possibly replace the clutch plates?
Have you checked the gearbox oil?
Probably a good idea to change all the oils and clean the filters as it has been standing for a while.
There should be a seal on the footrest shaft which would have been cork originally (part  66-4902). The chaincase should only be filled to the level plug,  my handbook says the amount should be 2 fluid ounces which is only about 60cc, if the case is overfilled then you are likely to get clutch problems.
The oil for the primary case needs to be a thinner grade than the engine oil, the handbook says SAE 20 oil, although using automatic transmission oil is a possible option.
You can probably get a photocopy manual from Bruce Main-Smith:
  http://www.brucemain-smith.com/
Looks like the manual you need is = 642/AVERY/1124 for '46-'53 models.
  

[douglas mccullough]

 i cant beleive your even interested in such a machine with your naivety. this is gong to be a disaster for the next restorer in line after you have probably stuffed any of the remaining restorable parts on this bike! go slowly and find out i.e read about the mechanical consruction get a workshop manual and save another bike from butchery.  douglas

[BSA_in_NZ]

Hi I have a b31 that is fitted with triumph piston and 30mm carb  which increased the power output