Export thread

I pulled the plug wires to find out which one wasn't firing

Checked the compression: 85psi non-running cylinder / 90psi running cylinder
Checked coils: both making sparks. switched plugs
Popped valve cover: all valves moving
Removed carb and intake pipe: clear of obstructions

I'm not sure how more to trouble shoot this further. The cylinder that was running was very oily and there was oil sputtering out of the coupling between the exhaust pipe and muffler. The carb appears to feed both cylinders (plastic crossover pipe with "T" to the carb) so I think fuel is good. Should I blast a bit of carb cleaner in the dead cylinder?

I've read maybe dropped valve guide. I'm not sure what to look for. When I was manually spinning the crank with the intake off, the live cylinder puffed a bit back up the intake but I forget what position the valves were in.

I've had no trouble with the mower previously and it always starts 1-2 pulls. It started right up on the second pull today, but just ran on 1 cylinder. It is smoking a lot when running (on 1cylinder) like its burning oil.

I replaced a coil a year ago because the ground had corroded. When that happened I would turn the key off and the mower would run on 1 cylinder because one coil wouldn't get grounded. It was not smoking when that was happening.

Thanks in advance.

If you have on oily plug then you have got one blown head gasket or broken rings on one piston

bertsmobile1 said:

If you have on oily plug then you have got one blown head gasket or broken rings on one piston

Click to expand...

How can I diagnosis broken rings or head gasket? I thought that the compression check would have those items covered.

rpl3000 said:

How can I diagnosis broken rings or head gasket? I thought that the compression check would have those items covered.

Click to expand...

With all due respects, the problem is you are not thinking things through thoroughly.
Mower engines have automatic decompression at cranking speeds, thus compression figures are meaningless.
Doing regular compression tests will show when a problem is happening because you can follow trends of a sudden drop or a gradual drop or a difference between each side.
Because the decompressor is done via the valves, then changes in the valve lash will also change the absolute figures.
This is why we have to do the more complicated leak down tests to verify cylinder sealing.
80 psi is approaching the minimum compression that will allow an engine to fire which is what a decompressor is designed to do.

bertsmobile1 said:

With all due respects, the problem is you are not thinking things through thoroughly.
Mower engines have automatic decompression at cranking speeds, thus compression figures are meaningless.
Doing regular compression tests will show when a problem is happening because you can follow trends of a sudden drop or a gradual drop or a difference between each side.
Because the decompressor is done via the valves, then changes in the valve lash will also change the absolute figures.
This is why we have to do the more complicated leak down tests to verify cylinder sealing.
80 psi is approaching the minimum compression that will allow an engine to fire which is what a decompressor is designed to do.

Click to expand...

I'm here to learn.
So I took the check valve out of my compression tester and hooked it up to my air compressor to try to do a leak-down by watching the gauge on the air compressor. Both the live and dead cylinders are leaking on the exhaust valves quite a bit. I could watch the gauge needle drop on both of them. I had expected to unplug the compressor and come back in a few hours to see if the needed moved off the tape. (I made sure that I was at TDC)

Next suggestions? Are we at stage of pulling the heads for the leaky exhaust valves?

valve clearance was 0.012" on the live cylinder, and 0.011" on the dead.

Am I correct in that the clearance should about half that? (like 0.005")

0.004" inlet & 0.006 exhaust so about 1/3.

pump the cylinders back up and take off the , carb, mufflrt & dipstick
After you blow one up, have a listen for the Hisssssssss.
Hiss in the dip stick = rings
Hiss in the other places = valves.
You might want to block off the breather as well.

And we are all here to learn.

I pressurized the cylinders again and listened for leaks. I heard leaks from the intake/exhaust and oil fill for both cylinders. I now have a copy of the engine manual for this motor and the compression check procedure is on a warm engine, and the min psi listed is 57 [psi]. I imagine that this is accounting for the decompression bump. I'm not entirely convinced that the rings are bad because the motor is cold and the live cylinder has ring blow by too. Especially after when pulling the head, the bottom half of the gasket was wet and didn't separate when I removed it.


I also found one of the cooling passages pretty much completely blocked.


The exhaust push rod seemed a bit bent when rolling it on a flat surface also, but I didn't measure the runout yet to compare to the manual.

I think its safe to assume that the live cylinder head probably has the same level of cooling passage blockage. I'm going to try and clean that out w/o pulling that head too, but for another $10 gasket I think I'm going to pull both heads and get the valves ground and re-seated. Does this seem like a good game plan? What does a shop typically charge for this service?

I can still see hone marks on the cylinder walls and there is no scoring. This it too difficult to capture in a photo otherwise I'd post that photo too.

Your manual should be here http://www.mymowerparts.com/pdf/Kawasaki-Service-and-Repair-Manuals/

If the cooling channels were blocked then a better than average chance the head has cooked and will require replacement.
When over heated the valve guide shift as does the valve seat.

I had the heads checked - They were flat. Valve guides were not shifted. I checked the valves diameter. One intake valve was 0.001 under spec (I did not replace). I cleaned out the carbon deposits and lapped the valves (did not re-cut valves). Installed new head gaskets, valve cover gaskets and spark plugs.

I had a bit of oil smoke on startup but cleared up after 30 seconds. I coated the valve stems and was pretty liberal oiling everything in the top end so this wasn't too unexpected. I let it run for about 5 minutes at low idle before doing a few high idle cycles. Then I mowed for about 40 minutes w/o incident. It feels more powerful and did not bog a bit as expected. I hadn't mowed since about 9/13 so the grass was a bit tall.

I had been having a hot restart problem prior to the head gasket blowing. Now that I think about it more, I think this was probably an indicator of the problem. I think when the gasket blew (cyl #2) it was pressurizing the crankcase and breather, thus blowing a bunch of oil into cylinder #1.

I'm going to be more vigilant about keeping the cooling channels clear, but what is a good shutdown procedure? I typically let it sit at low idle for 2 minutes. I thought about running 1/2 choke to give it more fuel (and cool EGT, or at least that's how it works in auto engines) prior to shut down, but it seems its either full choke or nothing with mine, and full choke just stalled it out.

When you idle an air-cooled engine it gets hot. They are designed to run WOT to cool and perform the best. I just lower my throttle to 3/4 the wait the few seconds it takes to settle into that speed then turn it off.

I advise to shut the fuel off and starve the engine out.
The information in the previous post was spot on, air flow diminishes very rapidly with engine speed.
At 1/2 throttle you are creating about 3/5 of the heat you do WFO but only have 1/3 the air flow volume to remove it.

The last few cycles of the engine it will be running very lean and thus burn off any deposits on the plug so will start better.

A blown head gasket will always make an engine hard to start.
On mowers it drastically reduces the compression which allows the starter motor to spin faster which masks it to the untrained ear.