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 > Kohler 5CKM21 no compression in both cylinders

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Rigdon

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Posted: 09/16/21 06:27pm Link  |  Quote  |  Print  |  Notify Moderator

if the intake valve had pressure coming out instead of in then you have stuck intake valves on both cylinders. the trick with pressurizing the cylinder through the sparkplug works very well. Other small engines used to get carbon fouling in the valve guides resulting in stuck valves and no compression usually from the carb running rich.


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Gjac

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Posted: 09/18/21 10:46am Link  |  Quote  |  Print  |  Notify Moderator

Rigdon wrote:

if the intake valve had pressure coming out instead of in then you have stuck intake valves on both cylinders. the trick with pressurizing the cylinder through the sparkplug works very well. Other small engines used to get carbon fouling in the valve guides resulting in stuck valves and no compression usually from the carb running rich.
I pressurized both cylinders through the spark plug hole with 100 psi. At TDC air just rushed out of the intake, rotated fly wheel to different positions and compression built up no air coming out of the tail pipe or intake was noted . I went back to TDC and poured Chemtool into each spark plug hole and reinserted plugs and will soak the valves for a couple of days. At TDC I did not see chem tool leak out. May leak oy slowly. I still don't know how intake valves can just stick in both cylinders at the same time while the engine was running? I can see them sticking if it sat for a period of time without the engine running. Has anyone seen this happening before?

enblethen

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Posted: 09/18/21 11:48am Link  |  Quote  |  Print  |  Notify Moderator

If it has compression release like on Briggs, you have to turn back the crank a little to get valves to close. When engine RPM is high enough the compression release disengages.


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Gdetrailer

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Posted: 09/18/21 08:39pm Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

If it has compression release like on Briggs, you have to turn back the crank a little to get valves to close. When engine RPM is high enough the compression release disengages.


Not sure if Kohler has a compression release.

Found a parts diagram for a Magnum M20 HERE

Don't see any thing in the valve train that looks like any form of compression release which I would not be too shocked about. Kohler often didn't use compression release at least with the 1960s cast iron engines I have played with.

Sadly, I suspect OP may need open up and dissect the engine, kind of doubt this is going to be fixable via external means.

wa8yxm

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Posted: 09/19/21 07:55am Link  |  Quote  |  Print  |  Notify Moderator

IF the cylinders built up compression with the spark plug feed, nothing coming out intake or exhause or crankcase vent or (if water cooled) radiator...

I"m stumped

You need 3 things to varroom
Fuel and air mixed in the proper portion (Explosive mix)
Compression (Appears you got that)
Spark. (Gasoline engines)
Heat (Diesel)


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Gdetrailer

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Posted: 09/19/21 01:34pm Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

IF the cylinders built up compression with the spark plug feed, nothing coming out intake or exhause or crankcase vent or (if water cooled) radiator...

I"m stumped

You need 3 things to varroom
Fuel and air mixed in the proper portion (Explosive mix)
Compression (Appears you got that)
Spark. (Gasoline engines)
Heat (Diesel)


Missed a big item, "timing".

Everything must be done in the correct sequence one right after the other.

All it takes is timing to jump or valves to hang open slightly and it is all over.

Timing seems to be gear to gear, so no chain or belt, but there is a possibility that there could be a plastic or nylon gear in the mix..

Kohler isn't what it used to be and somewhere in the past I have read about a lot complaints of issues with many modern twin cylinder Kohler engines having valve related failures. If I remember correctly the valve guides moving out of place or valve seats causing the valves to not seal.

Basically I doubt the issue is fixable from the outside and will need some sort of teardown to assess the condition.

A bit more research, found some items for the OP to check..

https://www.lawnsite.com/threads/help-kohler-25-died-turns-over-but-no-compression.359856

Sorry, I was going to hot link but the forum doesn't like the URL above due to the formatting [emoticon]

From that website..

" Help! Kohler 25 died, turns over but no compression

Any ideas where to start looking for problem? Symptoms are like a broken timing chain would cause...just died suddenly, spins over freely with the starter, but acts like no compression (resistance). Happened late yesterday, so I haven't had a chance to investigate it yet. Any help greatly appreciated!

Here is what was wrong with mine. Engine ran fine. Shut it off and it wouldn't start again. Checked compression and there was none. Took the valve cover off and when turning the flywheel around by hand that one of the valves was returning very slowly. Sprayed some penetrating oil on the valve stem and turned the engine over and I had compression. Put the plug back in and it started right up again."


Very good chance the valve guides are gummed up and not closing quick enough..

Another which was mentioned in the link above, if you have a pressurized oil system seems Kohler in many of these engines may be using hydraulic lifters with the oil pump to create a compression release. Issues with the oil pump relief valve may not allow the lifters to release correctly to running position. Not sure how you test for that..

A broken crank gear was mentioned if the rocker arms are not moving which would mean replacement crank and cam shaft..

Need to at least pull the valve covers and see if the rockers/valves are moving correctly..

* This post was edited 09/19/21 03:43pm by Gdetrailer *

Gjac

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Posted: 09/20/21 11:01am Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

wa8yxm wrote:

IF the cylinders built up compression with the spark plug feed, nothing coming out intake or exhause or crankcase vent or (if water cooled) radiator...

I"m stumped

You need 3 things to varroom
Fuel and air mixed in the proper portion (Explosive mix)
Compression (Appears you got that)
Spark. (Gasoline engines)
Heat (Diesel)


Missed a big item, "timing".

Everything must be done in the correct sequence one right after the other.

All it takes is timing to jump or valves to hang open slightly and it is all over.

Timing seems to be gear to gear, so no chain or belt, but there is a possibility that there could be a plastic or nylon gear in the mix..

Kohler isn't what it used to be and somewhere in the past I have read about a lot complaints of issues with many modern twin cylinder Kohler engines having valve related failures. If I remember correctly the valve guides moving out of place or valve seats causing the valves to not seal.

Basically I doubt the issue is fixable from the outside and will need some sort of teardown to assess the condition.

A bit more research, found some items for the OP to check..

https://www.lawnsite.com/threads/help-kohler-25-died-turns-over-but-no-compression.359856

Sorry, I was going to hot link but the forum doesn't like the URL above due to the formatting [emoticon]

From that website..

" Help! Kohler 25 died, turns over but no compression

Any ideas where to start looking for problem? Symptoms are like a broken timing chain would cause...just died suddenly, spins over freely with the starter, but acts like no compression (resistance). Happened late yesterday, so I haven't had a chance to investigate it yet. Any help greatly appreciated!

Here is what was wrong with mine. Engine ran fine. Shut it off and it wouldn't start again. Checked compression and there was none. Took the valve cover off and when turning the flywheel around by hand that one of the valves was returning very slowly. Sprayed some penetrating oil on the valve stem and turned the engine over and I had compression. Put the plug back in and it started right up again."


Very good chance the valve guides are gummed up and not closing quick enough..

Another which was mentioned in the link above, if you have a pressurized oil system seems Kohler in many of these engines may be using hydraulic lifters with the oil pump to create a compression release. Issues with the oil pump relief valve may not allow the lifters to release correctly to running position. Not sure how you test for that..

A broken crank gear was mentioned if the rocker arms are not moving which would mean replacement crank and cam shaft..

Need to at least pull the valve covers and see if the rockers/valves are moving correctly..
Some good information here. My Kohler is 25 years old, only 420 hrs on it. It is a flat head engine( no over head valves) and if you look at the web site you posted the crank shaft or cam shaft with gears are obsolete, so if that is the issue I am out of luck. I am still hoping that if both valves sticking(which is confusing to me) that soaking head with Chemtool will loosen them. The oil pump relief valve is something I had not even considered, but that would make sense if oil is not getting to the hyd lifters then I guess both intake and exhaust would stay closed and if both stay closed the no air comes into cylinder so no compression takes place. I still have a call into the Kohler rep, he has not been much help but if I ask a specific question he will research it for me. So I can aske about how to check this valve.

OkieGene

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Posted: 09/20/21 12:34pm Link  |  Quote  |  Print  |  Notify Moderator

I think, if this were me, I'd call a Mobil RV Tech to come out and perform an analysis, and then go from there.

Gdetrailer

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Posted: 09/20/21 12:38pm Link  |  Quote  |  Print  |  Notify Moderator

Gjac wrote:

Some good information here. My Kohler is 25 years old, only 420 hrs on it. It is a flat head engine( no over head valves) and if you look at the web site you posted the crank shaft or cam shaft with gears are obsolete, so if that is the issue I am out of luck. I am still hoping that if both valves sticking(which is confusing to me) that soaking head with Chemtool will loosen them. The oil pump relief valve is something I had not even considered, but that would make sense if oil is not getting to the hyd lifters then I guess both intake and exhaust would stay closed and if both stay closed the no air comes into cylinder so no compression takes place. I still have a call into the Kohler rep, he has not been much help but if I ask a specific question he will research it for me. So I can aske about how to check this valve.


Yeah, looked like a lot of Kohlers parts are obsolete but, there may be some parts available through aftermarket brands like Stens.

Flat head does make some difference, no rockers, more a direct drive from cam to valve which simplifies things a bit but also still has the possibility of valve/lifter issue.

Doesn't take much valve hang to stop building compression.

Gjac

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Posted: 09/22/21 07:24am Link  |  Quote  |  Print  |  Notify Moderator

Update. I poured Chemtool into spark plug holes it did leak down somewhere. Maybe past rings because it is thin maybe down valves. The engine has opposing pistons which are horizontal. After two applications of Chemtool and soaking for 4 days I added motor oil and that seems to be holding in the cylinders. I am hoping if it is a valve being stuck this combination would free it up.

* This post was edited 09/22/21 07:44am by Gjac *

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