Kohler Courage Pro 25HP low power problem

[jccndakota]

Our 2012 Ariens Max Zoom has the Kohler Courage Pro 25HP engine, 380 hours. Last fall it developed a bad idle, high rpm miss and was down on power. This year I took it to the dealer for a spring service.

The manual said it was due for a valve adjustment so I asked for that also. When we got it back the condition was the same. So it has new fuel filter, plugs, air filter, etc. It fouls plugs pretty fast and has no adjustment on the carb. So I ordered a new carb from Kohler and put it on. It has idle adjustment and idles better. High rpm miss is still there. I decided to check for a vacuum leak as if it were a V8 Chevy. It doesn't respond to putting my hand over the carb opening so I put a rag into the carb opening with the engine running. It kept running so it seems to have a big vacuum leak. The intake manifold looks to be some kind of two piece plastic unit. It's hard to tell if it has a crack because of the design. Kohler sells it for $47.00 so I'm thinking of getting it. Does anybody know if this is common on these engines? I have lots of V8 experience but none with Kohler twins.


Thanks, JC

 

[tomplum]

Intake manifold issues are not common. Bursts of carb spray around the seam of the manifold could help detect a vacuum leak while you run it up. Going back to the fouled plugs, is it hard carbon such as from oil burning? That could indicate a breather issue on these or possibly a cylinder headgasket. But first you should know that it doesn't take much extra oil in a Courage twin for the breather to be unable to handle it. In fact if you have a thread in dipstick, check the oil level threaded all the way in regardless of what your manual says. Do not exceed *Full*
If it is a soft soot, rich running type of fouling, verify that the oil is not contaminated w/ fuel as well. That could be from a leaking fuel pump or dropping one cylinder as it is running- IE funky coil on one side or?