YZF450 dies

[dddracing]

Just rebuilt my YFZ450 after the piston broke. I replaced the crank and rod, cylinder, head and a stock Wiseco piston. It starts and runs for approx. 10 seconds then dies hard like it locks down, but it isn't locking down as soon as it dies you can crank it over freely. I have checked cam timing, and pulled the head off to make sure the piston wasn't hitting.
I am wondering if the one way clutch for the starter could be freezing up and stopping the motor. I would figure that it would just spin the starter if this happened.
Please let me know if anyone has ever ran into this problem, or if there is something electrical that could cause this.

[1fst400]

well it could be many things. But it could be somthing as easy as the float needle being pluged up in the carb.

A yfz will run for about 10 secconds on a carb full then die till the gas slowly fills it back up. My friends yfz does this all the time.

[250X_project]

You say it "locks down?" If it acting as it is seizing, then maybe it is. I hate to say it, but you may be going toward the same problem you had. Do you have good oil flow? An oil port may be clogged closing off the oil passage ways, to keep oil from the top end. Does it smoke or smell hot?

This is just a thought, though I would be more apt to think it would definitely run for more than 10 seconds. More like 10-20 minutes. Yet if this were the case it would obviously be best to catch early. ;)