. I changed my sons 100 CRF to 120 with BBR big bore kit. Allso I have hot cams, BBR exhaust, open inlet and 26mm Keihin carb. Piston rings are sure in right position and I have new valve (and all other) gaskets.
Works well, but eat oil much (blue smoke and dark blakc spark plug).
Oil dispose is so much that I have to add oil 100cc after every riding session.
Whats wrong
I do engineering myself (have made many bikes before) but this one is big question