yz450f won't crank after rebuild high comp. piston

I have ask this earlier but can't find the post. I installed a je high compression piston in my 04 450f today and it will not even attemp to crank. the cam timing is perfect, the compression is great, and the plug is firing outside the cylinder (ngk cr8e) the carb is great the bike cranked great just before I did the topend but now will not even backfire.

HELP PLEASE!!!!!!!!!!

Engines need 3 things to run. Spark, compression, air/fuel. One of the 3 your missing.

Engines need 3 things to run. Spark, compression, air/fuel. One of the 3 your missing.

Has spark..

Has compression..

Had a good working carby but perhaps something happened in reasssembly at this air fuel mixture point..

Engines need 3 things to run. Spark (at the right time), compression, air/fuel. One of the 3 your missing.
Your troubles are most likely the result of bad fuel, a carb problem, or an old plug, but it might be worth your time to check the flywheel key.

check stop switch button

Thanks to all. It is fixed. The flywheel key was the problem. It had fallen out and the ignition timing was off.

Thanks for all the help.

Your troubles are most likely the result of bad fuel, a carb problem, or an old plug, but it might be worth your time to check the flywheel key.
Thanks to all. It is fixed. The flywheel key was the problem. It had fallen out and the ignition timing was off.

Thanks for all the help.

and his legend continues to grow...

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