I just bought this unit on ebay as a barely used machine. I am pretty sure it was a demo unit as it came in the box and there was barely a scratch on the machine. Anyway, I have used it a few times and everytime it would start up fine and work but it always felt like it wasn't giving me its all at high speed. The last time I had it out the more i used it the more the engine seemed like it wanted to quit on me at full speed but it would idle fine. To me it seems like i need to adjust the high speed but I can't find one. After researching this carburetor (Zama RB-K106) a little bit it seems like there isn't a high speed or it is covered inside a plug. Do you agree that it seems like the high speed adjustment needs to be played with a bit? How hard is it to adjust? I doubt I have any warranty on the unit since I bought it on ebay so taking it to a dealer I would get charged an arm and a leg. Would buying a new carb for $20 bucks fix the problem or will it just be the same issue? Any advice will be appreciated!!!