Hello to all I've just purchased a bultaco 159 project, which needs a hole lot of work.

It's stripped now and I'm working out what I need.

I think it's a 350 can anyone tell me the piston diameter so I can work it out for sure.

Thanks Ben

Hi Ben,

159 is a 350 (or actually 325ccs).

Not sure of piston diameter but the 250cc version is 70-72mm so if yours is in the 80's it'll defo be a 350.

cheers Stu

Good luck with the rebuild. I'm rebuilding an M80 and I've had a lot of excellent advice from the guys that know a lot more about Bultos than I do.

Best advice I can give is don't be afraid to ask.

The bore of the 325cc engine is 83mm, stroke is the same as the 250cc which is 60mm.

Check the engine number stamped on the right side crankcase, the first 3 numbers tell you which type it is, if it is the correct type it will start 159, same as the frame, the remaining numbers may match the frame but not necessarily as they sometimes differed when new.

The original standard bore of a 325cc sherpa is 83.20mm

BUT your engine could or could not have re-bored to a bigger size over the years

and necessarily be still on the std bore.

So you will need to measure the bore to see what piston size you need.

ta

Edited December 1, 201114 yr by pedronicman

Thanks for the help everyone. I will get the micrometer on the piston in work today.

I got the case split last night in work and it doesn't look to bad.

The engine number is a 159, matching numbers.

It needs new rod bearings so I'm going to make a jig for splitting the crank and re pressing back together.

I will get some pictures up on hear soon.

Unsure what to do with the frame yet. I was thinking of ripping off a puma style bike but I'm not sure yet?

Any idears would be a great help

Thanks again Ben

Just had a look at the barrel and piston

84mm

That's had a bit take out of it.

I take it you can get rings for 84mm ??

Just had a look at the barrel and piston

84mm

That's had a bit take out of it.

I take it you can get rings for 84mm ??

yes