K301 Sputters When Revved Over Half Throttle

[KK560]

I've mowed with it at least 3 times so far this season without any problems until now. I've cleaned the carburetor, changed points, condenser, coil, regulator, check the spark plug, tried different plug wires, adjusted the governor, and it's still not wanting to run full throttle, once it's warned up after 5 minutes or so. What else should I check?

 

[ILENGINE]

Try applying a small amount of choke to see if it smooths out which could indicate an air leak between the carb and the block. Also the old K series had issues with leaking head gaskets when hot. Would run fine when first started and then would start cutting out to the point the engine would die in some cases until it cooled off. Normally occurred after removing the head for other work and not replacing the head bolts.

 

[KK560]

Try applying a small amount of choke to see if it smooths out which could indicate an air leak between the carb and the block. Also the old K series had issues with leaking head gaskets when hot. Would run fine when first started and then would start cutting out to the point the engine would die in some cases until it cooled off. Normally occurred after removing the head for other work and not replacing the head bolts.

The choke didn't make a difference. I'm pretty sure the head gasket wasn't leaking, because it was still getting good enough compression I could turn it by hand and hear/feel it. I also just took the head off to see if there was carbon built up, which there wasn't and no signs of compression passing the fire ring on the gasket. I've also noticed I'm getting consistent power on the negative side of the coil with the key on, engine off, no matter the stroke.

 

[KK560]

I adjusted the points to .016 and that seemed to take care of it...for now.

I can't see how I'd have that problem this time when there weren't any issues the last time I ran it, unless it had several all at once.