Hard to tell how much or how little of that is M20...I suspect very little. The cylinder head looks odd and although it is not clear if that is a separate gearbox if it is it doesn't appear to be M20....In fact the tappet plate looks like the most 'M20' part...even the barrel doesn't look M20, either in shape or with the small diameter exhaust which exits the barrel horizontally. And it is not vertically mounted.
Is this a completely different bottom half that already had electric start(Japanese perhaps, possibly Industrial?))with a sidevalve top end fitted ? (perhaps a 250 or 350?)
It also sounds a bit 'revvy' for an M20 indicating it may have a lighter crank.
More info. would be interesting....Ian
Hi Ian, that's pretty much what I felt. Too revvy. Sounds like a short stroke. I figured it was a Honda bottom end (or similar). Also, when the starter spins, I can't imagine that an M20 lump would sound that way (I imagine an M20 would sort of lump slowly over TDC, and then graunch down until it fires).
It looks like a SOHC top end reworked to imitate a sidevalve. Not sure what I think of it. Interesting and amusing? Pointless? Step up for an M20? Step down for a Honda? I'd also be interested to see more if the owner watches this forum.
Phil Pearson over in Gt Yarmouth can fit an electric start to your M20! He has made up a special frame to mount the starter inside the primary case. I dont think you have to alter the cases either.
Cheers, Mick.
Yes I believe that is true Mick, a mate has a 500 single Goldie, DBD, with an electric start and the decompresser has to be pulled in to allow the crank to get a good rotation before releasing to fire. I don't think they are cheap.
Yes, I did a feature on Phil for Classic Bike magazine and he showed me the electric starter. I'm not sure if it would attach as readily to an M20 with tin primary cases. I think it relies upon the alloy cases for support.
He has made a frame up that fits inside the primaries to take all the loading without relying on them to support the starter. It came about because an old boy round here has a prewar outfit, an M23 I think. He could no longer start it, so asked Phil to help out, which he did.
Cheers, Mick.