I Have a 1988 300TRX It runs but is very rough running. Electrics ok, carburation ok, any ideals?

Question

We have tried replacing all electronics such as a CDI coil, plug, plug wire etc. We actually took a carb off of a twin bike that ran great and installed it on mine and no difference. Check the valves and ok, checked the compression and ok.

Answer 1

Check the valve timing, and put the plug wire on a plug which is outside the engine and grounded, then crank and see if it sparks.