I have a 05 KFX 400 I rode into my shop to put on new tires a week later it would not start. I checked the oil it was full of gas. now it has only 30 PSI compression and will not start. I rebuilt the carb and stopped the gas leak. Does anyone have any ideas why I have lost compression besides a scored cylinder.

Thanks

 

Have you sprayed any oil into the intake while cranking her over? If gasoline washed all the oil off your cylinder walls, the rings have hard time creating a tight seal on dry walls.
It is a simple test to do during a compression check and it can rule out the rings fast.

 

Yes I did put oil in the cylinder. It didn't help. I'm afraid it's scored a piston.

 

Not necessarily.
Have you checked your valve lash/clearance? Tight valves will definitely create a low-compression scenario.

One thing I wonder is why you are seeing this change all of a sudden.
Though sometimes the explanation is "crud in valve seats". It happens on occasion. Maybe the overabundance of fuel in the cylinder loosened some crud off your piston top and it made its way through the valves and some got stuck in the seats? Only time will tell.

I am sure someone much smarter than me will chime in soon.

 

Valves are a good idea I hope to check them in a week or so it was - 5 here today so I will look closer when it warms up. Thank