richin your low end thats proberty what it is ,and make sure your idle is about 1.5 open where it doesnt turn the wheels when its started. i had nothing but problems with the force engine i coulnt tune that thing at all it would never say running. also i knoe the engine is new but check the carb bolt to see if its tight dont overtighen through . and check for leaks around the engine espially around the carb i had a leak around the carb on the force and i did put sealing around it but it still wount run worth of crap.