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Just rebuilt top end and have no compression (Help)

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Today I did a top end on my kx250f... I replaced the head, both cams, all valves, springs, gaskets, so on and do forth

When I was all finished up, the bike was timed, and everything all closed up I kick it over and have no compression at all. The only resistance on the kick starter is coming from the valve springs when the cam shaft lobes press down to any of the valves. The bike won't start and I know that compression must be the issue. 

My question is, what can be the cause of no compression... Could the valves being out of time be the cause of no compression? 

Thanks TT

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5 hours ago, skorpan777 said:

Did you thigh down that sparkplug? 

It can be forgotten sometimes 

Yes the spark plug is tightened down, also, whenever I move the kickstarter and I have the head cover off everything looks like its moving properly, but I can hear and feel air pushing upward, what can this indicate? Valve guide seals maybe, or valves just need shimmed? 

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If your timing marks are indeed correctly aligned, then check you valve clearance.

That is always to be done when you replace valves, cams or even if you disassemble the valve train and reuse it.

Hopefully the different valve train components didn't create significantly reduced valve clearance, and cause valve to piston contact.

Always check your valve clearance before you kick the motor over, and even then roll it by hand slowly so you can feel any contact and stop before any damage.

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