any ideas???
 

Hey everybody. Hows it going? I recently got a used 4 stroke xmotos 125cc pit bike. it was a good price but needed work (mostly aesthetics). The bike had a fair amount of surface rust on the frame so i stripped it down to the frame to do some rust treatment and repaint the frame. the motor, carburetor, and other parts were removed but not taken apart at all. i was planning on cleaning up the carb and tuning up the bike after. anyways, after repainting the frame, put motor, carb, tires, etc. back on and now i seem to be getting little to no compression at all. The bike started up and ran fine after one crank previously. Any ideas what might be causing this problem? Im not a mechanic and im using this cheap bike as a project. any help would be appreciated. Thanks for taking the time to read this and for any input. Have a great day.

Check valve clearances. How long has it sat during your resto? The clearance might have been too tight and a little rust or carbon on the stem could be causing it to not close. There are millions of good diy videos on line and you might find one for your engine. But the bottom line is learning engine basics. Compression loss can indicate valve leaks, worn rings, blown head gasket, cracked head, loose head bolts. You’ve gotta learn if you don’t want to pay someone else. I turned 78 today and have been playing with engines for 70. Good luck.