If your clutch arm is hitting the carb. before it clutches the engine you have either major wear on the flat surface of the clutch camshaft that pushes the bucking bar inward to disengage the clutch or the bucking bar itself is wore on one or both ends.
I say pull the clutcharm/chain gear cover off and inspect the lower part of the camshaft to see if it has a groove wore in it where it contacts the bucking bar and if not then take th bucking bar out and look to see if the 8mm ball bearing that it rides against have dished out the center of the bar, if it has then go to the local Tractor supply or hardware store and get a bolt that is either 5/16 or 8mm in diameter and about 3 inches long so it has an area between the threads and the head of the bolt that is long enough so that with a hacksaw or other means of cutting it you can use a piece of the unthreaded section of that bolt to make you a new bucking bar by cutting a section out of it that is the same length or maybe even a few .001's langer than the original bar.
I have done this on one of mine and it makes a better bucking bar than the ones that come in these engines in my opinion.
One or both of these two things I discribed here are likely your problem/ or problems from my experience.
If you need a clutch arm camshaft Piston Bikes has it here for $3 Motorized Bicycles Gas Bike Engines Gas Powered Bikes Motorized Bicycle Parts
They also have the new bucking bar for $4
Motorized Bicycles Gas Bike Engines Gas Powered Bikes Motorized Bicycle Parts
I dont understand the bucking bar costing $1 more that the camshaft which is machined to make verses the bucking bar just being a piece of junk round bar that isnt normally even cut true on the ends......... but anyway I say check these points and I'll bet you find your problem.
Good luck, Peace
Originally Posted by 210Don
I've done about 34+- round-trip. My first trip, i didn't have a derailleur so i had a ton of chain slap and my tire would grab the chain and pull it off the sprocket, it was pretty dangerous. I installed the derailleur and the second trip was smooth. The only issue i have now is not being able to fully disengage the clutch as the carburetor on my china girl impacts with the clutch arm. i plan on bending it so it clears... any other suggestions on that?