# Carb cleaning nightmare!



## Ed_GT5000 (Sep 30, 2003)

My Kohler Command CV12.5 was running great but the carb looked dirty so I thought I would pull it off and give it a good cleaning. No problem I have done this many times before and the result was a better running/starting engine. The cleaning was uneventful. lots of crud on the outside not too bad on the inside. I used Gum out and cleaned it out good. 
After getting it back together I hopped into the seat to take her for a spin around the yard- it would not start and was popping out the carb.
so I pulled the carb again, recleaned it reinstalled it and same thing backfiring out the carb.
I have two identical machines so I swapped carbs still won't start.
Now I am getting worried.

so this it what I do:

swap voltage regulaters nothing
pull flywheel check key good
drain gas and fill with fresh nothing
pull valve cover valves are working good.

I am running out of ideas. the engine ran great before I cleaned the carb I am now second guessing myself so I call it a night.

In the morning I try it again and nothing so I tear the engine down an do a valve job and now it runs great again..... the intake valve was not seating good and took a lot of lapping to clean it up.

I learned a good lesson-- if it ain't broke don't fix it!


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## Ed_GT5000 (Sep 30, 2003)

Well it seems i am not out of the woods yet. I mowed with the tractor and it will run fine and then sputter and die. It did it 3 times in the 40 minutes or so I used it. it does not happen often and can happen whether under load or not. Sometimes it starts right back up and sometimes it is hard to start but when running it still runs great. I did some on line research and this is a common problem with this engine. that is a bad coil that acts like a fuel/valve/timing issue. Funny though the intake valve did not seem to be seating right from the wear pattern on it, I am wondering if this was because it was sputtering and popping from a possible bad coil? BTW this engine did sputter and die once before when I first got it home and was test mowing with it. 
Please feel free to chime in with advice. I really don't want to swap coils and I have a volt meter but I am not sure if there is a way to test a coil that way.


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## Mickey (Aug 14, 2010)

From your description my first though was a timing issue which could translate to a coil problem.

Since you've done some checking and found this a a somewhat common issue and is typ the coil, I'd focus there. Coils can be checked with a multimeter and you check the resistance for the windings. Don't have any numbers you should be seeing so can't help there. I'm not familiar with this engine but I wouldn't overlook the trigger for the coil.


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## Ed_GT5000 (Sep 30, 2003)

I also see that the plug in this unit is a NGK and makes a bright whitesh spark when I try a champion out of my other kolher there is a weak whitesh spark not the blue spark I would expect


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## Ed_GT5000 (Sep 30, 2003)

I did a lot of searching on testing coils and found there is no definitive way to test for an intermitent problem. That said, I installed a new coil and mowed for an hour with no problems. It is much cooler weather this week so that could be a factor. I'll keep my fingers crossed on this one.


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## ErnieS (Jun 1, 2011)

I don't know if you can get at the coil without a lot of trouble, but the best way to troubleshoot intermittent electrical parts like a coil or ECM is by cooling the suspect part.
Go to Office Depot, Staples, or someone who sells computer supplies and get yourself a can of air. It's sold for blowing crud and dust from fans, keyboards, etc.

The can comes with a tube to direct the spray. What you want to do is hold the can upside down so that you spray the propellant at your coil. A couple seconds should do it, then wait 20 or 30 seconds for the temp to stabilize and try to fire it up.


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## Ed_GT5000 (Sep 30, 2003)

Ernie: that is one that i have not heard of and could save a lot of trouble.
I tested mine with a ohm meter and got 9. one thing I read said it should be 2-5. They say a high reading indicates a bad coil. But I kinda wonder if that is a good test. another test which I think is a good one is with an adjustable spark tester. I want to get one of these and they don't cost too much.
Here is the procedure:



eHow
Home & Garden
Garden & Lawn
Lawn Mowers
How to Test the Coil on a Kohler Command

How to Test the Coil on a Kohler Command
By Yvonne Grant, eHow Contributor

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Kohler Command engines are manufactured in both single-cylinder and twin-cylinder models. Single-cylinder engines have one coil, while the twin-cylinder have two. The coil generates the electricity or spark to the engine. Each coil is located beside the engine's flywheel above each spark plug. The prongs protruding out of the coil pass by the magnets in the flywheel creating electricity. If the coil malfunctions on a single cylinder, the engine will not start and the coil needs replacing. If one of the coils malfunctions on a twin-cylinder, the engine will run poorly. Testing the coil is a simple procedure that will take 5-10 minutes to complete.
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Things You'll Need

Spark tester

Instructions

Single-cylinder engine
1

Place the engine on a flat surface. Remove the key from the ignition.
2

Disconnect the spark wire from the spark plug located at the front of the engine. Plug the spark tester into the spark plug wire. Clip the other lead from the spark tester to the end of the spark plug.

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3

Set the spark tester gap to 2.0 mm by twisting the adjustment screw on top of the spark tester. Start the engine and watch the window on the tester. You should see a strong blue spark. If the spark is erratic or non-existent; the coil is malfunctioning. If there is a strong blue spark move to the next step.
4

Shut off the engine and adjust the spark tester to 8.0 mm. Start the engine. If there is still a strong blue spark the coil is operating at optimal performance


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## ErnieS (Jun 1, 2011)

Ed_GT5000 said:


> Ernie: that is one that i have not heard of and could save a lot of trouble.
> I tested mine with a ohm meter and got 9. one thing I read said it should be 2-5. They say a high reading indicates a bad coil. But I kinda wonder if that is a good test. another test which I think is a good one is with an adjustable spark tester. I want to get one of these and they don't cost too much.
> Here is the procedure:
> 
> ...


My test works for just about anything that has a heat related intermittent.
I had a motorcycle that would start up just fine, run 5 minutes and quit. If you let it sit for a minute, it would fire up and run all day. Let it sit much longer and it either wouldn't start at all or run 5 minutes and quit. It took a while to figure it out. I ended up using both the canned air *and* the wife's hair drier on the ECM. I found that there was a small temperature range (somewhere around body temperature +/- 5 degrees or so) where the damned thing wouldn't trigger the coils. I ended up with an aftermarket ignition system that gave me a few more ponies for less than the stock Harley Davidson ECM.


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## Ed_GT5000 (Sep 30, 2003)

I Think the problem is fixed. I mowed again for over an hour and it ran great even using the champion plug that had a weak spark with the old coil. I can sure see how a bad coil can be hard to diagnose! I have heard of coil problems like this but this was the first one for me. I have had coils fail before, but in those .cases the engine had no spark at all


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## Argee (Sep 17, 2003)

Great thread Ed! Gives everyone a little education and insight on coils and what to expect! :thumbsup:


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## beachblu (May 21, 2012)

Thanks to all contributors on this threads. Very useful.


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## Ed_GT5000 (Sep 30, 2003)

UPDATE: Tractor is still running great!


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## Country Boy (Mar 18, 2010)

Ed_GT5000 said:


> I Think the problem is fixed. I mowed again for over an hour and it ran great even using the champion plug that had a weak spark with the old coil. I can sure see how a bad coil can be hard to diagnose! I have heard of coil problems like this but this was the first one for me. I have had coils fail before, but in those .cases the engine had no spark at all


Its probably not the coil that failed, but the trigger module that is built into the coil. The coil is just that, two coils of wire, one thick and one much thinner that generate the magnetic fields and the spark necessary for jumping the plug. Its basically a transformer. The trigger module replaces the points and condenser and is an electronic switch. When that "switch" gets faulty, it can become intermittent, not work at all, or fail at certain temps. I had a Stihl pole pruner that would start fine and idle all day, but when you'd grab the throttle to make a cut, it would die every time. Found out the spark was cutting out when the unit would accelerate. The module had a spark advance system built into it, and that was shot, so it would drop the spark instead of changing the timing when the trigger was pulled. I actually prefer the system that Kawasaki used (they might still use it) where there is a coil and a separate trigger module. Makes servicing the unit much easier when you don't have to pull the shroud to access the coil.

I generally replace all the points systems I run into with an electronic ignition kit for that very reason. I can mount the trigger module anywhere I want, so I put it in a very accessible spot so the next guy doesn't have to pull the engine apart to get at the module, unlike points which are usually under the flywheel on small engines.


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