Kohler SV840 shooting fire from only one exhaust pipe

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
I have a Dixon with a Kohler Courage Pro 27.

I have only had it for about 6 months, but it is about 10 years old. It has about 250 hours. It started losing power intermittently, then it would come back. I mowed with it doing this for a while. It would drop power for 2 minutes then run fine for 20 etc.

After a little trouble shooting I figured out that the spark advance modules was going bad intermittently on the cylinder that was dropping. I bought the replacement normal coils and installed them. Walla it runs great now....except I noticed after mowing after dark that mu muffler was glowing orange. The power seems fine.


I was able to see that the fire was only coming out of one of the exhaust pipes. I took the muffler off and flames are spitting out of the exhaust on the same side that the coil was bad on. There is only one carbonator so it would seem that it isn't the carborator being rich.


I adjusted the valves, and it didn't change anything. Re-gapped the spark plugs - nothing. swapped the coils, nothing.


Any ideas what to do next or what it may be. Did I damage the cylinder by running it while it was intermittently cutting out. Flame has only come out of one exhaust never the other.

Thanks. This is my first post btw.
 

bertsmobile1

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  • / Kohler SV840 shooting fire from only one exhaust pipe
Check the valve lash again.
Also have a good look at the valves, they are the same length so should stick out the same amount.
After that try a simple compression test see it the bad side is substantially lower than the good one.
Could be a burned or sticking exhaust valve.
If your engine has a diode between the two coils unplug it.
On some twins you get interfearence from one coil causing the other to throw a phantom spark.
Was the new coil an original item, an aftermarket one bought from a mower shop that wil stock good quality parts or the cheapest reject defective one you found on the web
 

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
It was the Kohler OEM replacement kit for the coils. It came in a Kohler box with what looked like Kohler instruction, but it was from ebay...I swapped them around with no change so I don't think it is the coil.

No diode between the coils.

I will do the compression test and if that doesn't show anything I will pull the head.
 

bertsmobile1

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  • / Kohler SV840 shooting fire from only one exhaust pipe
In that case it will most likely be the exhaust valve not fully closing or opening too soon.
 

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
I checked the compression it was 145 on the fire cylinder, it was 140 on the good cylinder..

I went ahead and pulled the head off. How do I tell if the valve is bad short of just replacing them. Also how do you check if the seat is good.
 

bertsmobile1

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  • / Kohler SV840 shooting fire from only one exhaust pipe
Easy way is to put an old plug in the head tip it upside down & fill it with fuel.
If any leaks past the valves, it is time for a valve job.
Visually inspect the valve any crack or split on the head or burned edges = replacement time.

Check "lapping valves" on U-tube.
thousands of videos of people doing it
 

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
Well my valves came in today. I attempted to lap them in. I put it all back together and it it still shooting fire. Don't know what to do next short of taking it to someone who does this for a living. Any Ideas?

It did look like the head gasket was blown also, I put a new gasket on it. Could it need a new head?
 

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
I still have the same issue shooting fire out of the first cylinder. The compression went up from 145 to about 152 with the new valves and head gasket.

I also took off the tube from the carburetor to the cylinders and checked for obstructions, clean. I sealed the top and bottom seams with epoxy to make sure it wasn't sucking air. Still no change.

Next I'm going to pull the flywheel and make sure the key is not messed up. It looks fine from the top.

Any other ideas?
 

bertsmobile1

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  • / Kohler SV840 shooting fire from only one exhaust pipe
If a new key in the flywheel does not do the job you can try moving the offending cylinders coil a little closer to the flywheel.
This will cause the spark to happen a little earlier.
IT should be 0.010". if it is more than 0.015" then that could have been your problem also if it is loose or touching the flywheel you can get funny timing.

Other than that you are left with the cam wearing funny.
Checking the cam ( roughly ) is easy.
Run a piece of masking tape right around the outside of the flywheel.
remove both spark plugs and bring the good cylinder up to TDC on the firing stroke.
Rule a line down the tape using the exit side magneto leg with a sharpie or similar.
Rotate the engine till the exhaust valve just starts to open and rule another line in a different colour continue rotating and do the same in the same colour when the exhaust valve closes and using a third colour mark the opening & closing of the inlet valve
Now go to the other cylinder, as you rotate the flywheel the lines you marked for the good cylinder should appear at the same places relative to the bad cylinders magneto.
Now they all might be a small amount ( say less than 0.050" ) out but that small amount must be the same for every event.
So if they all line up except for the exhaust opening &/or closing, the cam is most likely worn.
Now you can compensate for this by altering the valve lash on the bad cylinder.
Closing it down will open & close earlier but if you have to go smaller than .002" then the cam is toast.
 

Gatorbait7802

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  • / Kohler SV840 shooting fire from only one exhaust pipe
I pulled the flywheel, the key looked new. Blew the dirt out of it and put it back together.

I've tried the coils all the way out, in spec and too close, makes no difference in the fire coming from the exhaust.

I pulled the valve cover again. The valves did seem looser than I left them so I tightened them back to spec and it made no difference.

Next I put a dial indicator on each valve and checked the movement. Both valves stroke .350" I was going to put a cam in it, but this seems like the movement would be different if there was excessive wear. I haven't checked it by the rotation method that you suggested. This engine is mounted 90 degrees in the motor so clearances are tight to pull the valve cover on the other cylinder.

I also pulled the header between the carbonator and the intakes. I applied epoxy all along the seam on both sides in case something was sucking air. Didn't make a difference.

The flame is blue btw.
 
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