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25 hp Kohler on a 60" Gravely Zero turn.. low power under load with black smoke


gunner181's Avatar
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Join Date: Aug 2011
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08-22-11, 04:05 PM   #1  
25 hp Kohler on a 60" Gravely Zero turn.. low power under load with black smoke

Hello all

I am a newbie here and was wondering if someone might be able to help me out.
I have a 25 HP Kohler (1800 hrs) on a gravely 60" zero turn mower. Engine starts and idles fine, however when you start cutting and cut say more than 1/2 in the mower loses power and if you get into anything more you will feel the engine labouring and you see quite a bit of black smoke.. We did a compression test and it showed 150# on both sides. The one module/coil was replaced with no result..

I've also been told by a mechanic that this engine was tired and it just couldnt burn the fuel (which is the reason for the black smoke)
any help would be greatly appreciated!

Thanks

 
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cheese's Avatar
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08-22-11, 06:48 PM   #2  
150 psi on both cylinders says the engine is far from tired. Doesn't sound like a mechanic I would trust for much of anything. Black smoke is an indication of too much fuel mixed in with the air that is introduced to the engine. No matter how new or tired an engine is, as the amount of fuel mixed in the air becomes more than approximately 1 part for every 14 parts air, it will not fully burn the fuel in the mixture. This unburned fuel becomes soot, which is the black in your smoke. Try running it without the air filter and see if it improves (momentarily and not in dusty conditions). A clogged air filter or partially closed choke can cause this. If not, I would suspect you have carburetor problems. There is also a chance the fuel pump could be leaking fuel into the crankcase as well, but not as likely. Does the oil smell like gas?


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gunner181's Avatar
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08-22-11, 08:48 PM   #3  
Cheese

Thanks so much for the response.. I dont think the oil smells liek gas but I will recheck.. I will also try to run it without air filter for short period to see what happens.

Thanks again!

 
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