Hi Guys thanks for the info had a great chat with Alan Whitton & then Mick Ash both very helpful , My stumbling point is the head I just lost one to a fellow club member . I asked Mick about using a modified 350 head but from the problems he had it looks like a no go, My next plan is to talk to Alan again & see what size the bore of a Mick Dickenson barrel is pre machining & if will take a smaller liner with enough room a less modified 350 bolt patten without welding If it could take a 78mm id liner gives a 400cc engine with small ports & valves to keep gas speed up at low RPM a Honda CRF250 piston has been used by somebody to give me the best of both worlds .
Your thoughts as always are most welcome gentlemen.
Rgs Rob