I have a Ryobi 31cc that was converted with a Bowman ring and ei igntion. I cant seem to get the high end to tune out. It sounds like it is running rich all the time, ie it has a 4 stroking sound. Cant seem to get that nice 2 stroke sound. Low end is fine. idles and transitions good. Has a tecumseh carb. Only one I have ever seen. I have tried changing the timing but all that seems to do is make it harder to start. The motor is inverted. The spark plug has a nice tan color like it is adjusted properly. The Bowman ring probably has 2 tanks of fuel run time. Should I try running it more to let the ring seat in more or is this carb just junk? Any suggestions?

Thanks
Jim