Info on the 155z engine as to the z155 engine.

[Deangillard]

Hey all, I'm new to the info side of minibikes. I can change anything on or in these little engines but info side I'm learning. I have a 155z engine I'm just rebuilt, got a racing fly wheel and cdi but I'm after info on upgrading or big bore kit to fit my 155z. I also hear a lot say these engine and gearboxes are no good while othere swear by them. Plus how to tell if you have a z155OH or a normal z155. Many thanks