250 / 350 bsa engines

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I've been looking for a B40 (350) engine for a while without a lot of luck, and was re-reading the CDB article on Andy Roberton's bikes today. It says that the 350 engine he runs is based on a B25 bottom end.

So my question is, what engines could I use to build up a 350 if I can't find a complete B40? ie. what would be the best bottom end to look for, I've been told that some models have different bearing and oiling setups and are more robust as a result. Are the gearboxes and clutches the same across the models or are some better than other?

Cheers

[Marc.com]

I've been looking for a B40 (350) engine for a while without a lot of luck, and was re-reading the CDB article on Andy Roberton's bikes today. It says that the 350 engine he runs is based on a B25 bottom end.
Cheers

B25 according to my manual is closer to the B44, from memory Andy Robertsons 350 was kind of over bored stroked 250 using B44/50 top end, longer rod shorter barrel. So quite a bit of machining involved. B40 top end is completely different, ditto crank, etc.

Which begs the question why not use B44 engine in the first place. I guess the only reason to build a 350 like this is to stay within class rules or to build rev happy short stroke 350. The other bike Andy was running was big bore 500 beast, so guess they were running two classes.

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well, I suppose I was thinking a B40 for the following reasons

1. It's pre65 legal
2. I thought it might be cheaper/easier to find than a B44
3. After reading that article and talking to different people I thought the 350 might be easier to ride, given I'm not going to be up the pointy end of the field no matter what I'm riding.

But I was thinking today (which is a coincidence, given your question) that maybe a B44 isn't such a bad idea. I know it's not pre65 legal, but then the clubs up here lump the classes together anyway.

I'm wondering whether the B44 might actually be a better choice given it's popularity therefore more spares etc available? I'm assuming there were more B44's made than B40's?

Anyway, have you got a spare one

[LWC82PE]

There should be stacks of ex army B40's around. Have you tried asking some of the british clubs? Try the 'BSA owners club' You will find one if you try hard enough and they are not exactly rare.

I also have a B40 basket case engine  , but it will be missing parts, its all apart and some parts are rusty and dusty etc and there would still be more parts to source. I know there is the bulk of it there though and mainly missing things like odd shims, nuts, bolts, carby, maybe electrics and the odd trans/clutch part. I will try and work out whats there and let you know, but i dont imagine to be able to do that before the weekend. the only thing is that i dont know what year it is yet but im pretty sure its not a post 65 army one so you would probably be alright for pre 65 legalities there. Im my opinion the B40 is a good choice, quite reliable.

[Marc.com]

I'm wondering whether the B44 might actually be a better choice given it's popularity therefore more spares etc available? I'm assuming there were more B44's made than B40's?

as Leith mentioned the B40s were used by the army and sold off cheap. The B25 and B44 were a leap forward in technology (can't believe I said that ) or at least a newer more modern design which sported all alloy top end and begat the B50MX. I like the idea of a B25 as B350 by the way, just expensive way to get there.

Plenty of parts on Fleabay or available because the B44 was popular in the States and is still raced in the UK.
I like the B44, compact motor sitting next to TT500 and can be made to go well. I am building one with Carillo rod and big bore kit at the moment, oh and also alloy PES clutch, which addresses most of the engines weak points.... well apart from the gear box 

[jimg1au]

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a complete b40 sold on ebay 2 weeks ago for 1500.00 with new head and barrell
jim

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Cheers guys,

I have spoken to the local BSA club, and although the guy was pretty friendly, and actually had a B40 engine (in pieces, not an army model, not all the parts from the one engine, and definately needing a rebuild) I thought the $1500 asking price was a bit steep.

Dirtrumpy put me in touch with the secretary of the NSW club who was a wealth of knowledge. He gave me a couple of leads and websites/forums to look at. He seemed to think, as a couple of others have mentioned that $300-ish was more appropriate as an asking price for an engine that needed rebuilding?

There was a fully restored B40 WD in northern NSW that sold on ebay last year (when I didn't have the coin) that came with a spare (apparently rebuilt) engine, frame, tank, pipe, etc. The whole lot went for $2500. I'm kicking myself now, but there you go.

I suppose the main points are, I'm after something reliable and (relatively) inexpensive. I know that dollars have to be spent on these motors, but I don't want to start with the worst engine BSA ever made and try to make it better. I'd rather start with something reasonable and do the essentials to do to get it onto the track.

Cheers

[Marc.com]

Cheers guys,
I have spoken to the local BSA club, and although the guy was pretty friendly, and actually had a B40 engine (in pieces, not an army model, not all the parts from the one engine, and definitely needing a rebuild) I thought the $1500 asking price was a bit steep.

Yeah the BSA guy was getting a little friendly with the contents of your bank account.

You would have good runner B44 landed in Aussie from USA for that cash. If you can get one that is going OK already that would be worth spending a little more on.

http://cgi.ebay.com/ebaymotors/BSA-441-B44-VICTOR-MATCHING-S-BRITISH-MOTORCYCLE-PARTS-/220680053818?pt=Motorcycles_Parts_Accessories&hash=item33618e643a

[huskibul]

  i think the  army issue's came with the engine # -GA , apparently they have a roller bearing on crank  that other models dont that make it a better motor , in one issue of "classic dirtbike" Sir Jeff Smith refer's to the B-40 as a his favourite and refer's to it as a "happy motor "as opposed to B-44 & B-50 (his words not mine) Good Luck

[Marc.com]

in one issue of "classic dirtbike" Sir Jeff Smith refer's to the B-40 as a his favourite and refer's to it as a "happy motor "as opposed to B-44 & B-50 (his words not mine)

Isn't the B44 refered to as a 'happy motor' by Jeff Smith in VMX magazine, seems to be a lot of happiness out there. During the B40 era they seemed to still be racing Gold stars.

[huskibul]

  Correct me if i'am wrong but did'nt jeff smith win two world  titles on modifyed B40's of which the B44 was derived?

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Thanks to this forum and one of the members, it looks like I have a "happy motor" heading my way soon!

Woohoo! one step closer!!

[Marc.com]

Thanks to this forum and one of the members, it looks like I have a "happy motor" heading my way soon!

What type of happiness did you end up with finally, B40 ??

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Yes indeedy, a WD model to boot!

[huskibul]

  Good stuff paul ! maybe we will meet up on the pre 65 startline someday and compare note's cheers