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Q On Lgt 12 Kohler ...rough

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#1 Horvik OFFLINE  

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Posted October 02, 2012 - 09:57 PM


What are some of the reasons to make this engine run rough on idle? I already replaced points, and boiled out the carb. Tried adjusting the carb , both main and idle jet.
Speed the engine up, purrs like a cat.

Any ideas?

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Posted October 02, 2012 - 11:54 PM

I would remove the carb use the carb cleaner on it and do another clean job, replace the lines and make sure all fuel is flowing...then remove the head decarbon the piston top and head, reinstall it with a new headgasket...torqued to spec with a brand new plug. Make sure you have the carb tight so as to eliminate any potential vacuum leak. this will probably take you 1-2 hours to do the whole thing...I think you'll see a noticable difference...

#3 Grumpy ONLINE  



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Posted October 03, 2012 - 07:56 AM

I have had the same problem. What I found was dirt behind the 3/8 welch plug on the side of the carb. Remove the plug, clean and replace with a new plug. New plugs can be hard to find.

#4 boyscout862 ONLINE  

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Posted October 04, 2012 - 03:20 PM

The problem could be the valves. The tappet clearence is sensitive. If you're going to take the head off and decarbon it you might as well clean and lap the valves too. Then you can check and adjust the clearences.
Before doing anything else, just try adding an ounce of Marvel Mystery oil to the gas and running the engine for atleast an hour. You can pour a little MM into the carb while it is running too. It will remove alot of carbon and lubricate the valves and rings. I 've used it to increase compression and smooth out the idle. I add MM to the gas of all my engines because it helps them run better. Good luck.