Re: Bought a second hand engine/bike, having some problems
Can you see which main jet is installed? it's possible the previous owner put a bigger main in thinking it'll go faster.. Usually there's a number stamped somewhere on the jet telling it's size, you can also look at the jet opening to see is it looks like it was soldered and drilled or just drilled.
Check that the jet is mounted securely and not just sitting on there finger tight, check the needle and seat valve for any small debris that could keep it from shuting off. Also check the intake for leaks at the intake gasket, this can cause some intermittant issues if the intake gasket is leaking.
If everything else looks ok then check the base gasket, the case split line gasket, and finally, the crank seals, you can check these areas by running the engine at idle and spraying carb cleaner along these gasket areas and listen for any changes in the engine (reving up, slowing down, or dying) as the spray hits the gasket mating areas, if there's any change iin the engine that's where the leak is. You can chack the crank seals the same way but need to remove both covers then spray behind the mag rotor and the bevel gear while the engine is running, there should be no change with the engine unless you got a leak.