Kawasaki blowing smoke intermittenly, burning oil

I did a leak down test. The air in was running at 90 psi and the air going in held at 80 psi. No air sounding in the intake or exhaust. I could hear air going into the crankcase through the oil filler tube. I held my hand over the tube and felt very little pressure but could hear the air rush out when I removes my hand. From what I read a 10% reduction was acceptable.

I noticed my oil was pretty thin. I suspect some gas got into the oil before I replaced the carburetor. The oil did not smell strongly of gas and it would not ignite with a lighter but it was thin.

My exhaust valve was loose again so I reset it. I have had trouble with the valves loosening, not sure why.

I plan to put some frsh oil in it and see if that makes any difference.

Any suggestions?

My guess is possibly one or all of the rings but dont quote me on it,,just a guess.

I'm anxious to put the fresh oil in it. I'm hoping the thin oil was getting past the rings and building up in the valve cover. Any chance this could be the cause?

Oil that is too thin WHEN HOT will definately do that.
So you could start with new oil. New oil is always a good idea and neither hard nor expensive to do.
However I doubt it is the cause.
When I do leakdowns I usually go somewhere 150psi to 120psi.
The ides is to challenge the rings / valves.
At 80 psi you are at the lower limit acceptable compression pressures and in some engines will be insufficient pressure to cause ring sealing to occur.
Rings seal due to the action of compresses gasses getting behind them and forcing then onto the cylinder wall, not from their "Spring"

Yeah,I would throw some good old Shell Rotella 15/40 in it if it was mine....small engines love all that magnesium.

I went with the 15/40, no difference so I'm guessing the rings are going to have to be replaced. I was really hoping not to have to do a complete teardown! Question, when I replace the rings, is replacing the piston a must or only if I see a need?

Piston, rings, crankcase gasket and both seals is going to set me back about $150. I'm tempted to hold out and look for a twin cylinder air cooled Kawasaki and replace the whole engine.

arch252 said:

I went with the 15/40, no difference so I'm guessing the rings are going to have to be replaced. I was really hoping not to have to do a complete teardown! Question, when I replace the rings, is replacing the piston a must or only if I see a need?

Piston, rings, crankcase gasket and both seals is going to set me back about $150. I'm tempted to hold out and look for a twin cylinder air cooled Kawasaki and replace the whole engine.

Click to expand...

For me, the piston cost about the same as a full gasket kit and I never ever reuse an old gasket or apply silicone to an old gasket it is a no brainer to do the piston.
However do not order any parts till it is apart and you have checked the bore for ovality because new rings aint going to fix that.
The most critical measurement on your piston is the side gap between the ring and the ring groove.
Too big and it will leak past, too small and it wont pressureize.
After that is OK then check the wear on the thrust face and finally the play on the pin.
The latter two are not that critical on mower engines as they only spin at fairly low speeds.

Well keep us posted bro,,
I have had good luck with finding used engines on ebay or CL...I paid about $200 for a used FC 420V not long ago and its a great engine...most of the time they come out of home owner tractors with low hours on them.

Bert, I'm still struggling with this. I'm ready to accept that I need to replace the rings, BUT...

I ran the mower for about 30 minutes to get it warmed up. No smoke whatsoever and it ran fine. As soon as I saw the first puff of smoke I stopped the mower and removed the vent tube from the breather and stuck it in an empty coke can. I plugged the opening going into the breather. I ran the mower for about 20 more minutes. No smoke since the oil was going it the coke can and not the carb. I checked the can and in that short amount of time there was about 3 tablespoons of oil that had passed through the valve cover into the can.

If the problem were the rings, would the oil not be passing to the piston head and would the engine not be smoking like a freight train constantly?

Not to.mention the leak down test, albeit done at a lower psi than you would have done, indicated only about 10%

How does that much oil get forced up into the valve cover? There is no dislocation or residue buildup around the intake or exhaust valve guides so they do not appear to be bad, or at least bad enough to be allowing that much oil through.

I think I may have read enough to answer my own question. Oil is not coming up past the rings, combusted air is being forced down past the rings and building pressure in the crankcase, forcing the oil up into the valve cover past the reed valve. It's just taking mower about 30 minutes under load to build up enough pressure to start pushing oil out.

So... bad rings. Or bad cylinder.

Have I got it?