Help, Engine wont start. (yz426)

I bought this bike and it was not running. Seems like it has very little compression. I am just wondering where to start. Guy i bought it from said it just needs a cylinder/piston. Any suggestions will be helpful. Thanks (Its getting spark but will not even attempt to run.)

I'd check the timing and valve clearances first.

I've checked the timing to the best of my knowledge. Not for sure about valve clearances. Would a bad cylinder/piston or rings cause it to not even try to run?

I've checked the timing to the best of my knowledge. Not for sure about valve clearances. Would a bad cylinder/piston or rings cause it to not even try to run?

If there's no compression, it won't fire, so it won't run.

When you press down on the kickstart, do you get to a point where the kickstart won't go further, ie a hard point? If not, then you've got no compression, so either the rings or valves or maybe the valvelifter could be a problem.

be sure to check your valve clearances and timing chain tightness this can cause low compression and no starting. Then go from there

theres definitely no hard point when i press the kickstart, its looks as if the valves are operating correctly, i guess i will check the clearances and if that doesnt work move on down to check the rings/cylinder.

+1 on valve clearences, if a valve or valves are hanging open this will cause your problem.

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