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Open Roads Forum  >  Tech Issues

 > Kohler 5CKM21 no compression in both cylinders

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Gjac

Milford, CT

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Posted: 09/09/21 11:18am Link  |  Quote  |  Print  |  Notify Moderator

bgum wrote:

Did you pull the plugs to see if the pistons are moving up and down as they should? I know you said they were dry but did you check the pistons?
Put a plastic straw into spark plug holes and pistons are defiantly moving up and down. Also put a cap full of oil in cylinder and compression only came up slightly may be to 15 psi.

Gjac

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Posted: 09/09/21 04:14pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

You made it home!
I cannot find many drawings. Thing I did find is that you may have a "rubber" timing belt.
Timing belt
Would you check for any other model numbers on spec plate? Keep running into roadblocks on your number.
I spent several hours researching this and was convinced the problem was caused by a broken belt or slipped timing chain also, especially because nether cylinders had compression. I finally found a service manual and found that there is no belt or chain that controls timing but timing is controlled with an ignition module(coil) and there are no adjustments or points. Having said that I also noticed that there is a gap between the ignition module and the magneto. I replaced this module several years ago and set this gap to about .030 or so. I really don't understand how this controls the timing, but if the set screws loosened through vibration and the gap was smaller or larger would this change the timing? Would this have the same effect as a broken belt or timing chain slipping a couple of teeth?

Fisherman

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Posted: 09/09/21 04:51pm Link  |  Quote  |  Print  |  Notify Moderator

I spent several hours researching this and was convinced the problem was caused by a broken belt or slipped timing chain also, especially because nether cylinders had compression. I finally found a service manual and found that there is no belt or chain that controls timing but timing is controlled with an ignition module(coil) and there are no adjustments or points. Having said that I also noticed that there is a gap between the ignition module and the magneto. I replaced this module several years ago and set this gap to about .030 or so. I really don't understand how this controls the timing, but if the set screws loosened through vibration and the gap was smaller or larger would this change the timing? Would this have the same effect as a broken belt or timing chain slipping a couple of teeth?
Timing chain or belt controls the opening/closing of the valves unless it's a pushrod model. Ignition timing has nothing to do with the compression

bgum

South Louisiana

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Posted: 09/09/21 07:56pm Link  |  Quote  |  Print  |  Notify Moderator

Have you checked the lash on the valves both intake and exhaust?

Gjac

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Posted: 09/10/21 08:32am Link  |  Quote  |  Print  |  Notify Moderator

Fisherman wrote:

I spent several hours researching this and was convinced the problem was caused by a broken belt or slipped timing chain also, especially because nether cylinders had compression. I finally found a service manual and found that there is no belt or chain that controls timing but timing is controlled with an ignition module(coil) and there are no adjustments or points. Having said that I also noticed that there is a gap between the ignition module and the magneto. I replaced this module several years ago and set this gap to about .030 or so. I really don't understand how this controls the timing, but if the set screws loosened through vibration and the gap was smaller or larger would this change the timing? Would this have the same effect as a broken belt or timing chain slipping a couple of teeth?
Timing chain or belt controls the opening/closing of the valves unless it's a pushrod model. Ignition timing has nothing to do with the compression
My understanding is if the valve timing jumps, you'll get little or no compression equally in all cylinders, because valves fail to open and close at the right time. What am I missing?

DrewE

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Posted: 09/10/21 09:37am Link  |  Quote  |  Print  |  Notify Moderator

Gjac wrote:

My understanding is if the valve timing jumps, you'll get little or no compression equally in all cylinders, because valves fail to open and close at the right time. What am I missing?


You aren't missing anything there; however, the ignition module only controls the spark timing. It has nothing at all to do with the valve timing, which is affected by a timing chain or belt (if you have an overhead camshaft engine design), or by the camshaft in the engine block via pushrods.

If the gap you're talking about is between the pickup and the magnets on the flywheel: that gap does not affect the ignition timing which is fixed based on where the magnet is on the flywheel and where the ignition module mounts. If you can adjust the module clockwise or counterclockwise, that would alter the ignition timing. Likewise, if the flywheel slipped on the crankshaft (accompanied by shearing its key), that would also throw the ignition timing off. Neither of these in themselves affect the valve timing or compression in the slightest.





allbrandauto

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Posted: 09/10/21 10:21am Link  |  Quote  |  Print  |  Notify Moderator

how do you know the compression gauge is good when you crank it over with the plus in it does it sound like its cranking realy fast take a plug out and put your finger in the spark plug port and bump it over than you will know

Gjac

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Posted: 09/10/21 10:46am Link  |  Quote  |  Print  |  Notify Moderator

allbrandauto wrote:

how do you know the compression gauge is good when you crank it over with the plus in it does it sound like its cranking realy fast take a plug out and put your finger in the spark plug port and bump it over than you will know
What I did is check the compression on my lawn mower and got 65 psi so I know the gauge is good. Yes is spins really fast and can feel a slight pressure when I put my finger over the spark plug hole. In addition when I remove the air cleaner I feel no suction on the intake, instead it blows air out of the intake.

enblethen

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Posted: 09/10/21 10:58am Link  |  Quote  |  Print  |  Notify Moderator

I found a couple other manuals. They show overhead push rod type engine with gear driven camshaft off crankshaft.
I would pull easy to get to valve cover. Check to see if the valve rockers move.


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Gjac

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Posted: 09/10/21 01:14pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

I found a couple other manuals. They show overhead push rod type engine with gear driven camshaft off crankshaft.
I would pull easy to get to valve cover. Check to see if the valve rockers move.
Yes I know that would be the next step, it was raining all day yesterday and this morning I had a root canal done so hopefully get to it tomorrow.

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