Motor Locking Up While Trying To Start

new to the forum

i have a 2001 yz426 used from a friend when trying to start the bike after decompressing while kicking the motor wants to lock up

i took the screw cover off the lower unit and freed it with a ratchet and tried it againg done the same thing . any ideas

It's time to take it apart bro. That's the bottom line, if it were mine.

If it has an outside Cam chain adjuster try doing that before you open it up. My 450 cam chain got so loose that i thought my crank locked up. We pulled the whole thing apart to find that the cam chain had about 1" of play and binded as i was kicking.

If it has an outside Cam chain adjuster try doing that before you open it up. My 450 cam chain got so loose that i thought my crank locked up. We pulled the whole thing apart to find that the cam chain had about 1" of play and binded as i was kicking.

What I have noticed is that when the cam chain is stretched that badly it also does damage to the cam chain gear on the crankshaft, similar to what happens with the drive chain and sprockets. Once the teeth are sharp and bending over it's time for a crank shaft. This is just what I have noticed in the last few high hours motors we've dealt with.

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