166fmm 6 speed engine
 

I have been searching for an extra 165fmm engine for my x22R to do performance mods to and then swap it out for the stock one. I keep coming across the 166fmm 6 speed engine that says it has better performance. Does anyone know anything about the 166fmm? Is it bigger, faster, better gear ratio etc?

if you are talking about the Loncin RE250 that would almost be a direct swap. The Loncin RE250 is a counter balance engine so it does have a slight bulge on the front of the engine. Might or might not require a slight modification of the front lower engine mounting bracket.