Originally Posted by
Captcrunch44
SrTelemaster150
Are there any hop ups for a 120? like maybe a 150 crank.
Originally Posted by
Captcrunch44
i have some 120 parts I was going to mess with a little
You got the wheels turning.
FA-150 stroke is 27.5mm
FA-120S stroke is 24.7mm
That is a 2.8mm increase in stroke. Half of that increase would be 1.4mm increase in compression height or .055". Probably too much to prevent valve and/or head deck interference.
By using the C&H Ignitions .020" cylinder base shim you could probably remedy that situation by reducing the net increase in compression height to .035".
I have one of those shims somewhere if I can find it. You would still need to check head deck/valve clearances with .015" wax sheet. Crankcase clearance for the rod could also be a problem.
Displacement would be increased to 22cc or 1.34 cu in. I'm not sure what the CR would be, but it would be substantially increased over stock. If someone could link or post the Clarence Lee data on CR and combustion chamber size I could compute the CR.
Another option might be to swap the FA-150 conrod for the FA-120S item. That would only work if the journal diameter is the same and the C-C length of the small/large end rod bores is about .020"-.055" shorter for the FA-150 rod.