Engine Size 49cc called 50 72cc called 70 84.5cc called 85 86cc called 90 97.16cc called 100 107cc/108cc called 110 ______________________________________________________ Cubic Capacity in ml = bore rad.(mm) squared x 3.142 x stroke (mm), divided by 1,000 ______________________________________________________ Short stroke series 49cc = 39mm bore x 41.4mm stroke (C50, Z50, Jincheng 50) 72cc = 47mm bore x 41.4mm stroke (C70) 85cc = 51mm bore x 41.4mm stroke Long stroke series 86cc = 47mm bore x 49.5mm stroke (C90) 98cc = 50mm bore x 49.5mm stroke (Chinese 100 models) 107/108cc = 52.4mm bore x 49.5mm stroke (Chinese 110 models) 124cc = 54.0mm bore x 54.0mm stroke (Chinese 125 models) ______________________________________________________ There are 3 basic engine types: 1) 6v contact breaker/points model. Jincheng JC50Q-7 (Easy Rider M50/D/M/etc.) Panda, Singa etc. uses the 6v breaker/points model, only it has CDI ignition. 2) 12v CDI model. Honda. 3) 12v CDI C90 model (long GB5 cylinder) Honda, Jialing JH90 ______________________________________________________ There are 6 basic head types: 1) 49cc 6v head. 2) 72cc 6v head. 3) 49cc 12v head.(small valves GK4 head) 4) 49cc 12v head (large valves) 5) 72cc 12v head. 6) 89cc 12v head. (GB5) This is important for the piston type! ______________________________________________________ 6v or 12v cylinders are all the same.