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Kohler M 18 Running Super Rich


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#1 916 hydro OFFLINE  

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Posted May 06, 2013 - 10:51 AM

i have an m18 kohler on an 1810 cub cadet it is running super rich with the needele all the way shut or open will only run wth part choke and idles very high any suggestions?



#2 JDBrian OFFLINE  

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Posted May 06, 2013 - 11:16 AM

If the needle isn't affecting the rich condition then there is likely something plugging a jet or a stuck float or some other issue inside the carb. I'd pull it off and give it a good inspection/cleaning. Could it be loosing ignition on one cylinder or have poor spark quality? I'd give it the once over and maybe that will turn up the culprit.



#3 916 hydro OFFLINE  

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Posted May 06, 2013 - 11:23 AM

 could a worn needle let too much furl in? ive had it apart and cleened it and everything looked fine. could a bad fuel pump overload the carb? 



#4 JDBrian OFFLINE  

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Posted May 06, 2013 - 04:53 PM

Given the symptoms I'd check out the spark as well to make sure both cylinders are firing. If it's only running on 1 cylinder the gas that's going into the second one will not be burnt and will end up in the exhaust. A bad set of points will make the engine misfire due to poor spark and it will appear to be running rich as it is sucking in the fuel but not burning all of it. I'm not sure which jet you are adjusting. If it is the high speed jet then it won't have much affect on the idle speed mixture. I've never had one of the twins but I know that a bad float valve seat or needle will let fuel flood the carb. Not sure what type of fuel pump you have but the type that runs off the cam shaft can leak into the crankcase and that is not good. If your oil smells like gasoline then that needs fixing right away. 

  Someone with more experience with the magnum twins should be along to help out with more specific advice. 



#5 Canawler OFFLINE  

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Posted May 07, 2013 - 09:04 AM

Are you sure it's not lean instead of rich.  If you have to choke it to keep it running, it's probably not getting enough fuel so you're having to also cut down on the amount of air entering the carb.

If that's the case then look to your fuel pump.  I have an M18 in my GTX and had that happening intermittently after it got hot.  I would mow for 20 minutes or so then it would start running bad and I had to choke it to keep it running.  Shut it off, let it cool down and it would be good for another 20 minutes.  I found several reports on the internet of this problem with the Magnum 18s and 20s and it ended up being a bad fuel pump.  One of the check valves would drop out of it's seat when the body expanded from the heat and would be held again when it cooled off.  With the shrouding on the Magnums, I would have had to pull the engine to replace the pump so I installed an electric pump.  It's been good to go ever since.


Edited by Canawler, May 07, 2013 - 09:04 AM.


#6 916 hydro OFFLINE  

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Posted May 07, 2013 - 07:11 PM

im thinkin fuel pump i may also check to see if its leaking intake gaskets






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