been researching electric start options for 1985 200X and the Lifan engines come up often. Anyone have experience with this option?

 

The best way to know is to pull them both apart and do some measuring. See if the cylinder base gaskets are the same, measure the diameter of the main bearings, and the width between them. Also verify that the clutch side of the crank is the same as well as the flywheel side. Also make sure there is clearance in the crank case if the crank has a longer stroke. Most of these are made from similar honda casting's, and should be completely compatible, but like said before there might be a little difference here and there. The best way in my opinion would be to pull both apart and than do a mock up with the 4 speed cases and 110 crank, cylinder and piston to see if the crank spins freely. If so than i'd put it together and give it a go. You also might consider running the 110 flywheel as the timing points for spark might be slightly different if the 110 has a longer stroke. Realistically though It looks like the 50 and 70 cc models share the same stroke, and the 90 and 110 share the same stroke. The cases appear to be the same for a 50-125 looking at parts online. so it should be a pretty straight forward swap if main bearing diameters are the same, and the ends of the crankshaft are the same.