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I have a mid 1990s Craftsman lawn tractor with a Kohler CV15S engine. Background: 1) Had a small oil leak this spring. 2) Used tractor 2 times this year. First use while starting, it didn't start on first try and then sprayed fuel out of muffler. Then started and ran for 2 hours. Suspected fuel shut-off solenoid was bad. On second use after about 10 minutes, engine backfired and quiet. It would start but only ran at sub-idle speed regardless of throttle input.

Disassembled top half of engine, replaced carburator with new one. Replaced head gasket, Valve cover gasket, to fix oil leak and new carburator gaskets. Reassembled with new spark plug gaped to 0.040. Now engine does seem to fire at all. Checked fuse and interlock switches. Checked spark on engine block and check ignition module gap. Sprayed gas and and even starting fluids in carb. Still doesn't fire. I should also note that I can hear the engine intake pull air in when I turn engine. I am pretty sure the engine is getting fuel. Tested to carb and spark plug looks wet too. Noticed that valve lifters are non-adjustable type. However, it looks like the top valve, which I believe is the intake valve, is being depressed some even at its high point in the cycle. I suspect that the exhaust valve is also depressed some. I believe this is why it is not firing. Need help on what to do with this issue and what to do next.

Did you bleed off the hyd. lifters before you put it together?

Thanks for the reply.

No, I didn't bleed off the lifters. Was hoping I wouldn't have to do that.

Can you describe the process? I'm a bit of a novice with some of this work and I have never bled off the hydrolic lifters before. (I've done gaskets and carbs before but no lifter work.)

What tools will I need to compress the spring and bleed off the lifters?

Go to the Kohler service manual on line and it will tell you how to bleed off the lifters. As for myself I take each lifter and mount a old push rod in my drill press and press all the oil out of them. You could do the same thing with a vice and a bolt if you don't have a drill press.

Thanks. I assume that I will have to take the head back off to remove the lifters. Right? Any special tools or techniques to remove them?

kbm123 said:

Thanks. I assume that I will have to take the head back off to remove the lifters. Right? Any special tools or techniques to remove them?

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I don't know about the single cylinder Kohler command but on the twin cylinder command you can pull out the lifters through the head push rod holes. I use a magnet to remove the lifters. It looks like the same lifter they used in the GM car engines for years and they give very little problems.

reynoldston said:

I don't know about the single cylinder Kohler command but on the twin cylinder command you can pull out the lifters through the head push rod holes. I use a magnet to remove the lifters. It looks like the same lifter they used in the GM car engines for years and they give very little problems.

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Thanks for the suggestion. I'll take a look at it.

Just a thought... Did you check the key on the flywheel? Some of what you described sounds like it might be a timing issue. Good luck.

No I haven't checked the key yet. I don't think it is timing though because of the way it originally quit on me. I could be wrong but I'm not sure how timing would get out of sync without some sort of catastrophic failure. Again, I could be wrong. Just a novice at this.

Two things shear the key.
1) sudden violent stop
2) backfire
Well 3 if you add a loose flywheel bolt but that usually only happens after some one has removed the flywheel not during use.

kbm123 said:

No I haven't checked the key yet. I don't think it is timing though because of the way it originally quit on me. I could be wrong but I'm not sure how timing would get out of sync without some sort of catastrophic failure. Again, I could be wrong. Just a novice at this.

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You may able to inspect it from the top to see if the slots on the shaft and flywheel are aligned. I suspect that your timing is fine given that change in timing often leads to violent backfire, etc.

Have you checked compression? It should put at least 60-70psi. I suspect that the valve clearance needs adjustment.

c5vettster said:

. I suspect that the valve clearance needs adjustment.

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Now you are trying to confuse me. Just how do you adjust hydraulic valve lifters? This is the very reason I suggested bleeding off the oil in the lifters. Yes the GM cars they had a adjustment but I never seen it in a Kohler engine. I don't know everything and willing to learn.

reynoldston said:

Now you are trying to confuse me. Just how do you adjust hydraulic valve lifters? This is the very reason I suggested bleeding off the oil in the lifters. Yes the GM cars they had a adjustment but I never seen it in a Kohler engine. I don't know everything and willing to learn.

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The valve lash is adjustable. The procedure is described in their service manual which can be downloaded from their website

c5vettster said:

The valve lash is adjustable. The procedure is described in their service manual which can be downloaded from their website

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Very good I just left out the details. Now the OP has something follow. When I was working at a GM car dealer the lifters looked just like the Kohler lifters. I would dare to bet they are interchangeable? I put many camshafts and lifters in them older Chevrolets because they would flatten out the cam lobes. The newer cars now have gone to the roller lifters and better lube and seem to last forever.

reynoldston said:

Very good I just left out the details. Now the OP has something follow. When I was working at a GM car dealer the lifters looked just like the Kohler lifters. I would dare to bet they are interchangeable? I put many camshafts and lifters in them older Chevrolets because they would flatten out the cam lobes. The newer cars now have gone to the roller lifters and better lube and seem to last forever.

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I would suggest checking the compression first.

kbm123 said:

. Noticed that valve lifters are non-adjustable type. However, it looks like the top valve, which I believe is the intake valve, is being depressed some even at its high point in the cycle. I suspect that the exhaust valve is also depressed some. I believe this is why it is not firing. Need help on what to do with this issue and what to do next.

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This was the question asked

To get a engine running and I would assume this has been all checked out with the proper tools and skills. Spark, Fuel, Compression, and timing. If not start from the beginning.

c5vettster said:

I would suggest checking the compression first.

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Yesterday, I spent some time simply making sure I had fuel flow through my carburator. That all checks out fine. I have compression. It concistantly tests at 96 psi. I was able to get the engine to run at a sub idle speed but the throttle has no effect. I would say that it ran, anemically, at about 1/4 of normal idle speed. Not sure why it does this. Kind of points back to a valve or timing issue. That will be my next stop.

c5vettster said:

You may able to inspect it from the top to see if the slots on the shaft and flywheel are aligned. I suspect that your timing is fine given that change in timing often leads to violent backfire, etc.

Have you checked compression? It should put at least 60-70psi. I suspect that the valve clearance needs adjustment.

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I have 96 psi for compression. I also thought the valve clearance might be an issue but my compression doesn't seem to indicate that.

kbm123 said:

I have 96 psi for compression. I also thought the valve clearance might be an issue but my compression doesn't seem to indicate that.

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That is a very healthy compression indeed. One way to troubleshoot your fuel delivery is by removing the carburetor than try to start the engine on the spray of starter fluid/carb cleaner. If the engine revs up fine, your problem is in the fuel delivery/linkages. If the engine continues to run half-heartily - I would replace the ignition coil since it is an inexpensive item.

Alternatively, look for a used Briggs I/C engine. They are often sold for next to nothing on the CL and are decent to run and easy to work on.

kbm123 said:

I have 96 psi for compression. I also thought the valve clearance might be an issue but my compression doesn't seem to indicate that.

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An exhust valve that does not open will give a really good compression reading, but wont work.
Check the exhaust and the muffler .
Not very common on mowers but small furry things do decide the muffler makes a good home then die in there and block things up.
When your exhaust is blocked up you don't run at full speed either.
have you tried manually working the governor to open the throttle fully ?

I will check the muffler tonight. Worth a shot. Exhaust valve and intake valves are opening and closing. I was able to observe them through the spark plug port via fiber optic camera last night. Even though I installed a new carburator, I am going to recheck the idle speed needle for the correct position. .