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Old 09-12-2009, 11:13 AM
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LawnMower LawnMower is offline
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25 HP Kohler Command Pops, back fires and misses under a load.

25 HP Kohler Command on a Bob Cat, Pops, back fires, and misses under a load. This happens at all engine temps. It almost seems like a bad valve.

We did a compression check and were getting about 190 pounds on each cylinder.

The exhaust smells like its running lean. I cant find any screws on the carburetor to adjust the mixture.

It could be a coil problem, but I'm not sure how to check for that.

Any advice would be appreciated

John
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Old 09-12-2009, 01:51 PM
ricky86 ricky86 is online now
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I assume it is a CV-25. A twin Command will have about 150 psi when in good shape. I think your gauge is a bit optimistic or there might be a problem with the compression release (will have no effect on running but will be murder on starters) Get a service manual, and follow the instruction for checking the timing. There is a possibility that the spark advance system is a fault. Could be as simple as a loose connection. FOLLOW THE DIRECTIONS.
One word of caution, it is a C/D system and it will knock you on you butt if you get zapped. Extremely high voltage.
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Old 09-12-2009, 04:25 PM
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LawnMower LawnMower is offline
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Where can I get a manual? Isn't that some only the dealer can get?

Thanks for the response.
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401-749-0101
Newport
Rhode Island

2003 Ford F350 Dully V10 4+4
2003 Bobcat 61 inch ZTR, 25 horse Kolher
2002 Bobcat 54-inch walk behind, 17 horse Kawasaki
Stihl Back blower
2 Stihl strait shaft weed whackers
Stihl Chain saw
Little wonder hedge trimmer
Toro 22
9 foot Fisher plow
12+6 trailer
Red Max 8000 blower
Protero grass catcher for ZTR
Easy Dumper insert
water tank and pump set up for truck
Magna matic blade ballancer and grinder
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Old 09-12-2009, 04:51 PM
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I just checked and the Kohler web site has on line manuals that you can read right on the computer. Nice.
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401-749-0101
Newport
Rhode Island

2003 Ford F350 Dully V10 4+4
2003 Bobcat 61 inch ZTR, 25 horse Kolher
2002 Bobcat 54-inch walk behind, 17 horse Kawasaki
Stihl Back blower
2 Stihl strait shaft weed whackers
Stihl Chain saw
Little wonder hedge trimmer
Toro 22
9 foot Fisher plow
12+6 trailer
Red Max 8000 blower
Protero grass catcher for ZTR
Easy Dumper insert
water tank and pump set up for truck
Magna matic blade ballancer and grinder
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  #5  
Old 09-12-2009, 05:50 PM
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East Coast Lawn Choppers East Coast Lawn Choppers is offline
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You didn't say if it was a CV25 or CH25, but I have never seen one with a ACR (auto comp release) as far as the popping and hissing it can be a lot of things...
We just tore apart one that was using oil slightly and the #1 plug had become so oil caked that is was not firing good (but was firing) and it popped and carried on.
We have had some with burn't intake valves.
We had a few that had a worn lifter and lobe on the exhaust which forced the burn't gases to try to escape out of the intake on it's stroke.
We had one so far that the timing advance didn't work.
Carburation can also be a problem, pull off the carb and clean it, but I'd check a few other things first.
Do you have access to a leak down checker. If you fill the cylinder on compression stroke (or with the rockers off) you can see if it has a bad valve or bad rings.
It could be a lot of things.
The full maual, owner, parts and sevice are all online.
Let us know your results
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  #6  
Old 09-12-2009, 06:26 PM
PennaLawn PennaLawn is offline
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Just one thought fellows, I have had both engines, the one thing that I have found is the way Kohler runs there plug wires around the shielding on the engine has cost me 750.00$ IN A SHORT BLOCK! there are some really dumb rub spots that can cause a momentary short if the engine is under load. Check the entire lenth of both plug wires back to the coils and see if you don't have a bad rub? Just a thought.
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Old 09-13-2009, 05:20 PM
VegetiveSteam VegetiveSteam is offline
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What is the model number of your engine? The service manual is available at Kohlerplus.com. Click on enter as a guest and go to service literature. 190 lbs of compression is a little high but definitely not impossible. The Command twin doesn't have a compression release (except in special applications) so your minimum compression should be around 150. Typically they run 170 to 180. If I couldn't find anything like a bad plug or something simple like that I'd probably check the flywheel key. Not an extremely common issue but it does happen.
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Old 09-14-2009, 04:41 AM
topsites topsites is offline
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The other thing that comes to mind is the rubber pcv line...
Not sure if that particular model has one, but if it does, inspect for cracks / deterioration.

If that rubber pcv tube leaks air, the engine will run like crap, the symptoms vary, replace if in doubt.
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Old 09-14-2009, 10:41 AM
VegetiveSteam VegetiveSteam is offline
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Quote:
Originally Posted by topsites View Post
The other thing that comes to mind is the rubber pcv line...
Not sure if that particular model has one, but if it does, inspect for cracks / deterioration.

If that rubber pcv tube leaks air, the engine will run like crap, the symptoms vary, replace if in doubt.
I'm sorry to disagree with you on this but that breather tube, which this engine does have, will have no affect at all on how the engine runs. The only affect it would have is if you run the engine without it or with it cracked it lets the engine suck in unfiltered air and will eventually dirt gut the engine. Other than that the engine should run no different with or without that tube.
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Old 09-14-2009, 11:24 AM
JABBERS JABBERS is offline
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I had the same miss on my 26 efi kohlar with 1700 hours. This thing would come and go for 4 years finally i've had it. I replaced 1 coil which helped. My rocker arm came off that was fixed. Still had that same miss now and then so I replaced the lifters, I'll see today if its fixed.
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