Crank	Stroke	Wrist Pin	Crown Height	Cylinder Height	Flywheel Taper
Honda CRF50/70	41.4mm	13mm	18mm	63mm	12v
107 Import	49.5mm	13mm		69mm	12v
Takegawa	50mm	13mm	18mm	63mm	12v
Powroll Crank Rework	51mm	13mm	18mm	63mm	12v
Honda Trailbikes Stroker	51mm	13mm	18mm	63mm	12v
DrATV 'Monster' Stroker	52mm	13mm	19.5mm		12v
DrATV Stroker	52mm	13mm	19.5mm		6v
Lifan 125	54mm			79mm	12v
Takegawa R-Stage	54mm	13mm	18mm	69mm	12v
DrATV 54mm Stroker	54mm	13mm	19.5mm	69mm	12v
Lifan 120	55.5mm	14mm	19.5mm	79mm	12v
DRPuk 56mm Stroker	56mm	13mm	19.5mm		12v
GPX / Extreme 124	57mm	13mm	19.5mm	79mm	12v

Piston	Bore	Wrist Pin	Crown Height	Target Head	Target Compression Ratio @ Displacement
Honda CRF50	39mm	13mm	18mm	Honda 50	10:1 @ 49cc
Powroll 39mm	39mm	13mm	18mm	Honda 50	13:1 @ 49cc
Honda CRF70	47mm	13mm	17.5mm	Honda 70	9:1 @ 72cc
Powroll 47mm	47mm	13mm	17.5mm	Honda 70	11:1 @ 72cc
Powroll 'CRF70 80cc'	49.5mm	13mm	17.5mm	Honda 70	11:1 @ 80cc
Classic Honda 'Econno High Perf 88'	52mm	13mm	17.5mm	Kitaco 124SE
Honda Trailbikes '88'	52mm	13mm	17.5mm	Honda 50	11:1 @ 88cc
Honda Trailbikes '88 Race Head'	52mm	13mm	17.5mm	Honda 70	11:1 @ 88cc
Honda Trailbikes '108 Race Head'	52mm	13mm	17.5mm	Honda 70	11:1 @ 108cc
Kitaco 'STD / Ultra 88'	52mm	13mm	17.5mm	Kitaco 124SE
Theoretical 107 import	52.4mm	13mm		Honda 70	9:1 @ 107cc
AHP Minis High Comp 107 import	52.4mm	13mm		Honda 70	12:1 @ 107cc
DrATV 100034	54mm	13mm	19.5mm	Kitaco 124SE
Honda Trailbikes '117 Race Head'	54mm	13mm	17.5mm	Honda 70	11:1 @ 117cc
Takegawa '95 Super Head'	54mm	13mm	17.5mm	Kitaco 124SE

Crown height is measured from the top of the piston at the outermost edge, to the center of the wrist pin.

Cylinder Height is measured face to face and does not include the cylinder skirt.

Displacement: (pi / 4) * (bore^2) * stroke

Static Compression: (displacement + compressed volume) / compressed volume

CFM = (ci x RPM x VE) / 3456

CFM = HP x 1.62