I'm new to Bultaco bikes and have just bought a 1974 Sherpa 350T. It has an engine rattle which seems to be emanating from the cylinder. I've dismantled it and whilst the piston and big end and so on appear to be a wee bit worn they are all just within the tolerances given in my Haynes manual. Is this just the 'two stroke rattle' or should I go for a rebuild?

Edited February 14, 200620 yr by goat

I think one of mine is doing that too... Parts are available from Dave Renham at Bultaco UK. Rebuild is easy enough, as long as when/if you replace the main bearings you dont beleive the haynes book of lies. Ended up shipping my engine off to Dave to sort, put the new bearings in and assembled upto the point of clutch and mag, tried to turn engine over and it was locked solid. Haynes say heat the case (250 odd degrees IIRC) and put bearings on the crank and push home crank into case half, but this doesn't work. Heating the case and dropping the bearings into them does though.

If you anywhere near Kegworth/Nottingham/Midlands I can 100% recommend SEP in Kegworth as they do a top notch job and they do all kinds of engineering, crank rebuilds, rebores etc etc.

Pete

my `92 gasgas had a rattle like the one you mention.I replaced the piston with an oversize one and it cured the noise completely .

you might get away with replacing one the same size(without the wear).

Edited February 15, 200620 yr by gasgasssser

check the main bearings for crank motion up and down

Check the big end at various points around the 360degrees rotation. I have had engines with flat spot in big end that only appeared as loose at one particular spot. Looked great everywhere else.

thanks guys - I'l do bit more measuring and checking before I decide what to do.

I guess if I go for a new piston kit, connecting rod kit, and bearings all round I'm looking at