Big bore

[How1970]

Wanting to do a big bore kit. how do I determine the size of motor . Motor was given to me as box of parts. I got it back together. Runs ok but could use alot more

 

[Guest-19876]

what letters are on the crank? mine is an fm 80 which is a 38mm stroke with a high hole piston

 

[Street Ryderz]

Wanting to do a big bore kit. how do I determine the size of motor . Motor was given to me as box of parts. I got it back together. Runs ok but could use alot more

Porting and proper setup will yield more than the small gains of the over bores that are currently available. You can use a displacement calculator and input the bore and stroke to get the size of engine.

 

[Street Ryderz]

Always double check the rod your using. My FM80 is 39mm stroke.

The FM80 is supposed to be a 38mm stroke but I don't dough't it can be 39mm as they tend to vary a bit in the big end placement.That point 6 difference shown will make it 39.5mm oddly enough so yeah it's best to measure to know exactly what it is.