Tom, what sort of rebuild are you talking here? checking out limits and build up using basically all the original engine components or replacing all bearings,seals, big end, rebore etc regardless of condition?
Naturally you will want new seals and gaskets as a minimum, but if the gearbox is serviceable, the crank bearings feel tight and the piston clearance is within limits I could step you through doing the job yourself. I have built a few of these motors now and there are a few albeit significant pitfalls when assembling the kick starter mechanism and a few points of note when examining the engine cases for damage. Apart from that, you will only need a few basic handtools and a copy of the workshop manual to get the job done. No bother if you need to sub out stuff like bigend replacement and a rebore if required, most bike shops can offer this service even if they dont want to take on a full rebuild.
