BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: sidewaysid on 20 February, 2018, 17:11:24

Title: B31 head onto B33 Barrel
Post by: sidewaysid on 20 February, 2018, 17:11:24
Hi

I'm sure Andy Ingham can put me straight. I have a B33 barrel and piston but my B31 head won't quite fit, would it be fine to turn a little out of the diameter (it's only about 2 mm) is this common practice ?
Title: Re: B31 head onto B33 Barrel
Post by: sidewaysid on 20 February, 2018, 21:03:10
Sorry I mean Andy Higham, he seems to know a thing or two on the singles, I'm going to see if i can do that Suzuki clutch conversion like he has done.
Title: Re: B31 head onto B33 Barrel
Post by: ANDY HIGHAM on 21 February, 2018, 13:33:47
I would say even if it was possible it would be undesirable. The compression ratio would be high and the valve sizes smaller than the B33
Title: Re: B31 head onto B33 Barrel
Post by: sidewaysid on 22 February, 2018, 20:20:10
Andy you have put me right off putting a B33 barrel and piston onto my B31 engine, I am in the early stages of building my bike, I keep saying to myself it isn't going to be a concours winning example ( I have built these before, and have the trophies) it is going to be an old thumper to ride around the lanes, I did have a B31 swing arm model a long time ago, and it was a bit gutless, so i am thinking bump up the capacity (oh and bye the way I am not trying to emulate a Gold star, no interest) But with what you said Andy Higham, I have decided to go down the route of a T140 piston and overbore the B31 cylinder, I have 2 cylinders a small diameter fin and the large diameter fin, I'm going to use the large fin, it looks better suited to the head, I would gladly appreciate any help and constructive comments please, I am not a died in the wool BSA man, but I have always thought them solid as a rock since I had one to transport me to College in 1969, it was a C11G, what a lovely bike.
Andy I have purchased a Suzuki GS850 clutch, and would appreciate it if you could let me have some more detail of how you grafted it all together, I have a BSA centre hub, and I'm sure i have the clutch basket from an A10 or even a Triumph.

Please help
Title: Re: B31 head onto B33 Barrel
Post by: ANDY HIGHAM on 23 February, 2018, 12:39:41
Follow this link and there is a full write up of the modifications I made to my B31
http://www.britbike.com/forums/ubbthreads.php/topics/640945/b31-clubman#Post640945