kawasaki fr600v runs good but bogs down when under load.

i have a kawasaki FR600V-AS05 engine on a exmark lazer z turn zero, it starts and runs (in idle high and low) fine but when i start to move it bogs down. I checked for sparks and both cylinders/coils have spark. Here is what has me confused. I pulled the spark plug wire on the left side (by fuel pump )and mower runs just fine, put that back and pull the the wire on the right (by the oil filter) and mower dies. figured maybe a bad coil (even thought i have good spark on both), so i switched the coils and same results. Im very confused, i figured it should run if i pulled either spark plug wire just that it would run rough. I even switched the spark plugs around just in case but same results. Pull the wire on the left runs fine (until mower is put under a load by either driving it or engaging the blades) pull the spark plug wire on the right mower dies. Another thing that it is doing (not sure if related to problem but figure i mention it) is that sometimes when i turn the key on mower off the mower keeps running. i figure the coils are good, but not sure where to go from here, REGULATOR-VOLTAGE? COIL-CHARGING? mower was running just fine about a month ago when i last used it. Any suggestion as to what might cause the engine to die when i pull the

Have you checked compression on both sides

i have not put a gauge to it but plenty of power when i put my hand by the spark plug opening when i removed the spark plug.

is the plug wet is it getting fuel to the cylinder in question

yes plug is getting fuel.

ok you need compression above 50 psi. fuel and air mixture spark at the correct time

compression is 68 psi on the cylinder that has no affect when i pull the spark plug wire (the left one) and 74 or so on the right cylinder (one that kills the mower if i pull it). . i know im getting spark cause i tested the spark plug out side the cylinder and there was spark, also tested it with a spark plug firing indicator and it also showed continuous spark. By the way i appreciate your help and thanks for the suggestions. i ran the engine for 10 minutes pulled the spark plug on the left (one that has no affect on how engine runs) and it was wet with gas and a little bit of oil. the one in the right (one the shuts the engine off if i pull it) was completely dry.

I would suggest an air leak down test for ring wear or a blown head gasket

figured i check the valve see if they needed adjusting, i don't see any way to adjust them but when i took the valve cover off i had one bent push rod and the other rod was off the rocker arm. so ordering these parts and seeing where we are after that. Thanks again for all the help.

that will sure make it not run correctly. after you get parts with plugs out rotate by hand and compare valve lift on each side.