HS40 to HS50 flywheel swap?

[pdlsa10]

I have a 1978 HS50 with points, I want to use it on my 1971 Rupp. Is the flywheel from my Rupp's HS40 with a lighting coil a direct replacement onto the HS50? Any help would be appreciated. Thank you, Paul

 

[doubletrouble]

I would imagine they are, the main thing that changes from an HS 40 to HS 50 is the either the bore or stroke (dont remember). The exterior of the block is the same. Pull both flywheels off the motors and check them by measuring the diameter inside and out, the depth of the center holes and the flywheels thickness. Im willing to bet they can interchange. Do a test fit and give it a few pulls, if nothing crashes together give it a try.

Remember though the engine will need to be retimed - assuming you need to transplant the coil from one to the other. Its a little challenging. Timing requires a dial indicator with an L shaped end on it to reach inside the cylinder head thru the spark plug hole and touch the piston top. I improvised one by using a bent cotter pin attached to the end of my dial indicator, it worked fine.

 

[milo raptors]

the ports are bigger in the 50 to

 

[minibikedude]

HS40 and HS50 with points use the same flywheel between the two. Lighting coil flywheel part number for the both engines is the same 610769 Tecumseh P/N.