If you were to read back a ways, you will see I first built this plane with the Moki 1.8. Wit hthe tank in the stock position it was way to far away from the carb, I too couldn't get rpm's, even trying 3 different mufflers. I ended up using a Perry Pump on it and it worked great. Don't worry about weight, this plane can handle it. I took the Moki off and put a DL gasser on it and haven't looked back since.