1999 yz426f

My buddy has a 99 426 and last year the motor locked up on him, he couldnt even kick it atall, we adjusted the valves and it ran for about 10 mins and happened again. This time buying a entire new valve shim kit and installing it back to factory spec. The bike would crank over but wouldnt start, we jump started it and it started untill the choke shut of by itself. Jumped it again and it ran for a moment and locked up again, can hardly move the kickstart... Whete should i go from here

Im going to adjust the valves again but i no its just gonna mess up... Possibly break something worse, im getting really frustrated with the bike.

I doubt the valve gear has anything to do with this. A more likely problem is a rod bearing locking up on you because a faulty roller cage is allowing the rollers to become skewed.

ImageUploadedByThumper Talk1375199034.850987.jpg

And, BTW, there is no such thing as a '99 426. The '98-'99's were 400's. 426's were 2000-'02. Look at the front of the cylinder near the lower edge. The displacement will be cast in. There is a possibility that the cylinder has been swapped, however.

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