I bought a used gokart and have no knowledge of these things as it was for my grandkids. I thought it was nothing but a lawnmower engine that could take a beating and keep on ticking. Or like a Honda, all it needs is gas and oil. Well I am learning. It is a Chinese 110 cc. I have personally replaced the starter, spark plug and have taken the chain off of the rear sprocket and opened up the gear box twice, draining the oil and replacing, and worked with the gear shift to the clutch. I paid for a small engine repair person to replace the clutch originally and it did not run a week before it just stopped moving and this awful screetching noise of metal came from I now know to be the gear box and clutch. The repair person will not back up their work and I am limited with people that work on these gokarts, thus I have undertaken to see if I can repair or fix it using Google and YouTube. These have been informative, but I am not a mechanic......I am a lawyer. Now my issue is the gear shift device that fits into the gear box and engages the clutch will not stay in the slot on the clutch. The clutch sprocket goes around properly when the chain is disengaged from the rear sprocket and when just going through the shifting appears to be working. Put it back together, put oil in, and connect chain. Start engine and the metal screetching starts again, stops, shift gears and the sprocket does not go around. Get around to opening gear box up again and discover the device from the gear shift to the clutch has again come out of the slot on the clutch. Am I missing something. I have tightened the screw/bolt as much as can be. I am going to remove the clutch today and check the number of teeth on the sprocket just to see if perhaps the small engine mechanic put the correct clutch on the gokart.