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General Forestry => General Board => Topic started by: Southside on June 09, 2021, 06:46:27 PM

Title: Kohler is sick
Post by: Southside on June 09, 2021, 06:46:27 PM
So the 23.5 HP Kohler Command Pro (CH730) on my edger is sick.  Was fine Monday, didn't run it Tuesday, today when I went to run it all seemed normal, fired up, throttled up, tossed in the first 1.75" piece of dry pine and half way through the 12' board she sputtered, spurted, and died.  Gas tank was full, so I changed the fuel filter, scratched my head, and fired it right back up.  Did the same thing again so I got to looking around, air filter was clean, put in some Seafoam in case the gas had an issue, checked bearings, chains, etc in the event of a mechanical issue - found nothing.  

At first I thought it might be something with the governor so I put the Slither to all of the linkages and thought that fixed it - nope.  Eventually figured out that if I opened up the cut width so only one blade was cutting at a time it worked just fine, but when both are in the cut she dies down after a few feet.  Finished off what we had to do by cutting one side, then the other.  Shot the following video in hopes one might have suggestions  on where to look.  At first you see me feed the left blade, then the same piece of wood goes to the right blade - no change in the engine.  Then I adjust the width so both cut the board at the same time, notice how she dies down hard.  The air filter was off so I could look in case something strange was happening and I did notice a vapor coming out of the carb so you see me put my hand over it and sure enough my glove is wet and then dries right off.  That was the first time I noticed that so I checked the gas tank and sure enough she had gone through probably twice if not more the normal volume of gas for the time she ran.

So where do I start to look?  My thought is carb and or governor, not sure how much has to come apart to confirm the later is working properly.  Appreciate the input.  

Kohler not running right  (https://youtu.be/6IX9g7-waz8)
Title: Re: Kohler is sick
Post by: Patrick NC on June 09, 2021, 07:46:40 PM
The motor on my wood splitter was doing the same thing last year. There was a spark arrestor screen in the muffler that was plugged with carbon. Removed the screen and it's run fine ever since. Might be something restricting the exhaust
Title: Re: Kohler is sick
Post by: WV Sawmiller on June 09, 2021, 08:54:32 PM
   The 25 hp Kohler on my mill would start to bog down especially after running a few minutes and it turned out to be a bad coil. When it warmed up it was only running on one cylinder. I put a couple of ignition testers on from HF that cost a few $$ each and quickly found which one was sick. You might check that. Can't hurt. Good luck.
Title: Re: Kohler is sick
Post by: mike_belben on June 09, 2021, 09:38:19 PM
Temp gun on the exh ports will immediately indicate a dead bore.


A clogged up main jet, stuck float or stuck shutoff solenoid would reduce fuel availability and cause low power at WOT but i dont know if higher fuel consumption fits.


Timing light in the windshield wiper with a zip tie on the trigger is how i find erratic spark on vehicles.  


A bent valve will surely do it. Dust off your compression tester.  

Fuel spark compression.  Process of elimination.
Title: Re: Kohler is sick
Post by: YellowHammer on June 09, 2021, 10:11:13 PM
Check compression, it's probably fine, but I always check it first.  This also lets me look at the plug, and down into the bore.  May be as simple as a bad plug.


Check spark with an inline ignition tester, while it's running.

At this point, I'm thinking the carb may be flooding one cylinder, for whatever reason.  Look for a hole in the softgoods, or even a needle that isn't seating.  Something causing too much fuel flow.  I don't know the particulars of this engine, but that's what jumped out at me.  Especially since it took a while for it to happen, and seemed to be running soft, like it was way off its fuel curve.

Either that, or it swallowed one of the chickens I'm seeing in the background.  Does the exhaust smell like McNuggets?  

Title: Re: Kohler is sick
Post by: barbender on June 09, 2021, 11:24:54 PM
It sounds like a dead cylinder, ad much as I could hear. Or there is a chicken stuck in the exhaust😁 Also, I had an inkling that you may not be real well endowed in the looks department, Southside- the situation is actually worse than I thought!😁
Title: Re: Kohler is sick
Post by: WDH on June 10, 2021, 07:29:03 AM
At least the chickens were nice looking :D. 
Title: Re: Kohler is sick
Post by: Southside on June 10, 2021, 07:42:54 AM
Y'all are just jealous of my hat, and no chickens were harmed in the making of this video.   :D
Title: Re: Kohler is sick
Post by: Southside on June 10, 2021, 08:54:05 AM
200 PSI compression in each cylinder. Good spark, one plug looked carboned up, dry but more carbon than the other. Cleaned both, fired it up, she rolled coal for just a second, then tore apart 2" lumber. 

Guessing it was that plug so I ordered more just now. Will see what the day brings. 
Title: Re: Kohler is sick
Post by: mike_belben on June 10, 2021, 02:15:28 PM
I grind all my plug straps back and make the spark jump sideways, normal gap so as not to increase the workload on the coil.  

It exposes the spark to more fuel mixture molecules in the chamber and propogates the initial flame front quicker.  Almost like advancing the ignition timing without any detriment.  In microseconds, it gets the combustion spreading easier.  Cold starts are noticeably improved. 
Title: Re: Kohler is sick
Post by: Hilltop366 on June 10, 2021, 05:59:49 PM
Had a motorcycle in the shop that would run perfect under light load but when you tried to accelerate hard it would sputter and cough then work perfect again, turns out the carbs were partly filled with water so when running easy all was good but when running hard they would lower the level in the float bowl enough to suck up some water.

Dad use to tell me about the water injection in some planes (1950's USAF c119 is what he usually was in) that when turned on would set you back in your seat, apparently we were running a bit too much water in the motorcycle.
Title: Re: Kohler is sick
Post by: Southside on June 10, 2021, 06:06:55 PM
I will try that with the plugs Mike.  Do you grind them all the way back to before the bend?  Honestly it's been so long since I had a plug go bad that I had already ruled that out in my mind.  She ran great today and new plugs should be here tomorrow.  

Thinking about it can't remember ever changing the plugs in my 5.9's - guess I better do them too.   :D
Title: Re: Kohler is sick
Post by: newoodguy78 on June 10, 2021, 06:10:22 PM
Glad it was an easy fix 
Title: Re: Kohler is sick
Post by: barbender on June 10, 2021, 06:19:49 PM
I had a plug strap actually fall off (not long after I had been bragging on the Forum about never fouling or changing a plug in my chainsaws) and mash the top of a piston and head on my Jred 2171. I wanted to preemptively get rid of my plug straps at that point!
Title: Re: Kohler is sick
Post by: Tacotodd on June 10, 2021, 06:28:00 PM
Mike, that trick is something that I'm gonna have to try. It's very forward thinking of you.🙂 
Title: Re: Kohler is sick
Post by: mike_belben on June 10, 2021, 09:33:27 PM
I cant claim it.   its been around a long time in go fast toys.  Yes, i grind them just about to the elbow then tap tap tap the gap in.  


No sharp edges.  Round and smooth it all in nicely.
Title: Re: Kohler is sick
Post by: WDH on June 11, 2021, 06:22:07 AM
A pic would be nice.

Title: Re: Kohler is sick
Post by: Southside on June 17, 2021, 10:44:27 PM
Well she fowled another plug today - same one as the last time, things that make you go hummmm...Not EFI, so I can't see how the carb would cause the same plug to die two times in a row, thinking it's spark related.

Any way to test a coil and get a numerical value?  Clearly it's firing, but I wonder if it gets hot and has an issue or something else.  

Paging @sawguy21 (https://forestryforum.com/board/index.php?action=profile;u=1763) any ideas? 
Title: Re: Kohler is sick
Post by: mike_belben on June 17, 2021, 11:04:35 PM
Quote from: WDH on June 11, 2021, 06:22:07 AM
A pic would be nice.
Im sorry, i forgot about this.  Will try to remember to pull one out of something tomorrow.
Title: Re: Kohler is sick
Post by: pineywoods on June 18, 2021, 11:18:08 AM
Consider this possibility...The larger non-efi kohlers have a 2 barrel carb. One side partially plugged up.
Title: Re: Kohler is sick
Post by: sawguy21 on June 18, 2021, 11:36:29 AM
Then it would run lean. Have a look at the spark plug wire, it could be cracked and arcing killing power at the plug.
Title: Re: Kohler is sick
Post by: mike_belben on June 18, 2021, 10:21:36 PM
Quote from: WDH on June 11, 2021, 06:22:07 AM
A pic would be nice.

(https://forestryforum.com/gallery/albums/userpics/43722/0618211822_Film1-1.jpg?easyrotate_cache=1624068980)
Title: Re: Kohler is sick
Post by: mike_belben on June 18, 2021, 10:24:12 PM
Quote from: sawguy21 on June 18, 2021, 11:36:29 AM
Have a look at the spark plug wire, it could be cracked and arcing killing power at the plug.
X2. 
Run it, temp gun the exhaust runners. Swap wires, check cylinder temp again and see if the dead hole follows the wire.  Pretty good possibility if its got integrated coil and wire.  Ive had a few coil wires corrode off the coil stud under the jacket.  Its just a screw that the wire is threaded onto these days. 
Title: Re: Kohler is sick
Post by: Brad_bb on June 21, 2021, 01:54:48 AM
If you're starting it and runs pretty good, but after it starts warming up it dies, that may mean that as it heats up and things expand, something is happening due to the expansion?  In my case, my Kohler CH620 last summer blew a head gasket.  It would run at first, but as it heated up, the gap expanded.  If it's on the intake side, you'd be sucking too much air destroying the proper air/fuel ratio.  It will also affect your plug, because now you'd have a lean condition.  Just one thing to consider.  Changing the head gasket was not really a bad job at all.  I also cleaned all the soot from the head combustion chambers while I was at it.
Title: Re: Kohler is sick
Post by: Southside on July 10, 2021, 10:45:15 PM
Well earlier this week she fowled the other plug and my ignition tester showed both were good so today we tore into her.  Did not find much at first, but noticed liquid gas in the manifold under the carb after I pulled it.  Enough I could see it and soak it up with a rag, so figured the carb has to be flooding down.  The manifold isn't exactly symmetrical so I think it is possible that if she was flooding gas all this time it might go to the one cylinder over the other, until it got worse.  At least that's my working theory.  Everything else seemed to be fine.  

Could not see an obvious issue with any of the carb seals and such, but it would not take much so a rebuild kit is on the way.  
Title: Re: Kohler is sick
Post by: Southside on July 20, 2021, 10:15:23 PM
Well, as much as I doubted it at first it was the carb.  Been over a week and she is running strong, back to normal fuel consumption.  
Title: Re: Kohler is sick
Post by: YellowHammer on July 21, 2021, 12:12:09 AM
 smiley_thumbsup

Title: Re: Kohler is sick
Post by: newoodguy78 on July 21, 2021, 12:15:41 AM
Good deal 
Title: Re: Kohler is sick
Post by: Bruno of NH on July 21, 2021, 05:38:19 AM
Nice