Modification of your cylinder and cylinder heads (send us these parts  without valves)

 

140cm3 Why ?
1/ The diameter of the crankcase can't permit to do bigger than a piston kit 140. Boring the crankcase is very expensive.

2/ A larger displacement increases torque at low revs but would lose speed revving.
In fact the standard head  have very small intake and exaust ports adapted to a low capacity. It is impossible to obtain 10000rpm with a very big cubic.
We obtain an important gain, +30%, also by increasing the head exaust port so that the engine can breathe properly at high speed.

Warranty against defects

You must include look if you can do this sort of modification according to your local law.