I have this old 93 cr125 that I have entirely rebuilt, new piston, crank, bearings etc .. When I start it, it will crank right up but revs high, wont really idle at a normal level at all. This is in neutral, but if I hold in the clutch, it seems better but still way off. It has one of those funny keihin PJ carbs where the idle is adjusted by rotating the choke switch. I have adjusted the idle to the high and low of its range and the problem still occurs.

Ok the dumb question part .. I have not attached the chain yet, figured I would try and break in the motor (( Internal Combustion Engine ? )) first, then I recall reading somewhere that pilots and odys will rev higher than normal and even seize if the belt is not connected. Is this true for chain driven engines as well? I don't really understand how that would create an issue as the motor (( Internal Combustion Engine ? )) is in neutral, but at this point in my Engine rebuilding experience it seems there are several things that I am yet to understand.

nope chain don't matter except for the fact that a fresh Engine being rev should have a load against it.



usually those carbs are tough to idle not high rev. if your pretty sure its not or super lean or have an air leak then i suspect the throttle cable it too tight or possibly somebody messed with the carb and the slide isnt seating all the way down

Thanks Hare, that is what I was leaning towards, but I just wanted to be sure. The carb was pretty nasty before I cleaned it. It does appear to close all the way but maybe I will just replace it and see what happens.