I'm having problems getting the drive chain adjusted on my Grubee 49cc kit. When the bike wheel rotates the chain goes from about 1/2" free play to very tight every 180 degrees. I checked the driven sprocket and found the radial runout to be less than .003" with lateral runout of around .04". The only thing I can figure out is that I might have a bad sprocket. The chain rollers don't seem to seat in the bottom of the sprocket tooth gullets like they do on the pedal driven chain wheel on the other side. Anyone here have a similar experience and if you corrected it what was the cause? This conversion has been a pain due to overly close crank arms to the engine which caused me to mount the engine a bit higher than I'd wanted to which resulted in the need for me to heat and bend the exhaust pipe a good bit to get the muffler to clear the frame and crank arms. I haven't worked on the muffler problem yet due to the chain difficulty.