Do you know about the wildcat pk80? I have one myself and souped her up pretty good. Seems like a quality motor. Don't know what the stroke is or rod length or anything. I do know it uses a low hole piston though. LA Hover Bikes did a review on it and he measured a stroke of 38.9mm.
Im not familiar personally with the "Wildcat" PK80 but I have seen a couple listings on ebay for them.
I do know that over the years I have seen the engine geometry type I wnd others have called "the half breed" type engine which has a different crankshaft stroke and has extra wide crank counter balances.
These engines are 38mm stroke engines and are know to not have good port timing in stock out of te box form, but they run and some have said the balance on some of them is decent considering they all have bad balance without some crank trueing and some material removal on rod side of counter weights to compensate for weight of piston and rod weight.
These engines in my experience have been fairly easy to identify by all three or one or two of three different ways.
1.Connecting rod marked ZAE50
2. extra wide crank counter weights
3. with cylinder head removed, rotate crank until piston is TDC (top dead center) and you'll find that the top of piston is about .060" coming up flush with top of cylinder deck.
Now, I have an older "half breed engine" that has a crank that doesnt have the wider counter weights, but has the ZAE50 marked rod and had the issue of piston not reaching TDC like it should have.
To wrap this mini book here up..LOL
the only way I would know to tell for sure what the "Wildcat PK80" actually is would be to first pull head off and see if piston comes up to jug deck (correct TDC) of it does, then most likely you have a true PK80 geometry but doing a measurement of the stroke to see if tou have a 40mm stroke and also if you have a low pin piston will be ultimate way to know for sure what you have.
I hope this helps, this was the best way I knew how to explain it based on what I know from my dealings with these engines which I have been away from for a good while now.
Shan