Yz 125 2001 started then suddenly stopped and the kick start has ceased and wont move and when put into gear the back wheel does not move. took cylinder head off to check piston and the piston moves fine. after it started for 10 minutes then died again? thanks for any help.

IT NEED REPAIR , GEAR SHIFTING IS BAD.
FIND A SHOP AND GET IT FIXED/
MOVED THIS FROM CARS TO WHEEL CHAIR ELECT.

try to compleatly shift down then half up with the clucth in

contect me urgent 03452663007

Remove the spark plug, put the bike in fourth or fifth gear then try a jump start but with the key turned off. If the rear wheel locks up when you jump on and release the clutch then the piston has probably seized up OR the kick start-to-clutch hub gearing is messed up. The best thing to do is to remove the left engine side cover and look at the kick start mechanism. You may need to remove the clutch assembly for a full inspection. With the clutch removed the rotor ( crankshaft flywheel ) should turn. If it will not turn then a seized piston, broken cam chain or dropped valve is likely. If the rotor does turn then the kick start mechanism is the problem. Please rate my answer. Thanks!

take the case off and be careful not to drop any gears out the back of the case. Then snap the spring loose and then pull the kick axle gear out. The key is putting it back in. Carefuly line up the clip and square on the back of the kick axle with the holes in the back of the transmision then be sure to push on the gear to see if it popps into place. then bring the spring clockwise to fit into the hole. Besure the spring is pushed all the way back. Now carfully put the case back on.

You may have had a gear come apart and have a piece of it lodged in your gear box. Stop kicking on it and get someone to split the cases. No cheap fix here. Dump your oil and look for metal shavings. If you have shavings. . . you have yourself a $1500 problem. Also you may have somehow jammed your shifter hard enough to bend/break the shift fork. . . either way you have to split the cases to be sure.

Were you riding it when it jammed because that could mean the that something is sized inside the motor, like the crank or the pistion

Pull off the cylinder head. Look in the bore. Can you see seize marks on the cylinder? Nine chances out of ten you are going to have to remove the cylinder anyway, so go ahead and do it now. Did the piston seize up? Remove the left side cover. Rotate the flywheel. Crankshaft free to move now?

If not, drain the oil and look at it. Any metal shavings, cork or bits of ground metal in it? Remove the left side cover. Look at the kick start gear. Is it "locked up" in the clutch hub? Remove the clutch hub. Will the crankshaft turn freely now? Put the bike on blocks and turn the rear wheel. Will it turn? While the wheel is turning, can you shift into neutral? When in neutral, can you hold the clutch shaft still while the wheel turns? Any funny noises while the wheel turns?

The piston may have seized the engine. The kick start mechanism or a bent shift fork may have locked up the engine. Gremlins may have done it. Something did, so let's find out what.

Please rate this solution. Thanks!

check your compression I had a 94 yz that done that when i checked the compression it was really low so I put new rings on the piston and that's all it took to bring her back to life

I don't think this is a float issue. One way to check is to turn the gas off, take the bowl off the carb, hold the float up, and turn the gas back in. If fuel flows, the float needle is toast. It sounds suspiciosly like a worn topend, but it could also be a clogged jet ot fuel filter, or a faulty CDI.