Only one way to find out, you can't hurt a motor by going richer. If your plugs are black and oily, thats only for one reason, well, unless you mix a 10:1 premix, that might be a problem.
Hell, throw in a 300 and see what happens. I'd never say I'm an expert by any means.
One thing, you need to run your machine at wide open throttle in the highest gear you can get it in at high rpms, and kill the motor to check the plugs. This will rule in or out on your main jet. If its not oily, and its only oily at partial throttle, you might only have a pilot jet problem.