Small Engines (Lawn Mowers, etc.): kawaskai 2cyl water cooled fd620d, blown head gasket, rear valve

Question
smokes burns oil  rear plug fouls out front plug fouls a little compression is 190 on both cyls. oil on carb intake tube and some on hose to air cleaner leak down test about 4% on rear and about 3% on front cyl. can hear air and feel it coming out of rear valve pushrod channel none comes out of crankcase vent which is open can blow air into crankcase by mouth. when checking front cyl a little air comes out of the push rod channel not much. thankyou  

Answer
Well, this is complicated. On any other engine I would say on whichever cylinder has an oily plug you could have a blown head gasket, but on this engine the cylinder is surrounded by liquid. I suggest you perform your leakdown test with the rocker arms off the engine and rotate the piston from the top to the bottom and see if the reading is different. You may find some wear in the middle of the cylinder that doesn't show in your inital test. The air you feel coming through the push rod channel could be coming from the crankase.