Kohler CH25 S Mis

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  #1  
Old 12-08-09, 06:56 PM
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Kohler CH25 S Mis

Got a kohler CH25 S that has developed a miss that appears from around 2200 RPM to 3200 RPM (I don't run it above that). No miss at idle and when I put a load on the engine at 3200 the miss smooths out and the engine runs better.

This is what I have did so far:
1.) While running at 3200 RPM, pulled plug wire off each side and the engine died down each time.
2.) Replaced fuel filter
3.) Checked air filter (just replaced about 1 month ago), ran it without AF, same thing
4.) Checked plug gaps-right on the money, also just replaced about a month ago
5.) Replaced ignition module on one side, as one side had plug wire that had a nick in the boot thought maybe it was causing it to arc.
6.) Checked air gap in both ignition modules-right on the money.
7.) Replaced SAM, same thing....it will just not go away except when under a load and at idle.

I also noticed the plugs looked a little lean, that's what made me replace the SAM. I have 3 of these engines, one brand new that I am replacing and old one and going to use the old one for parts, so I can try just about anything. Anybody have any other ideas?
 
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Old 12-08-09, 08:26 PM
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Just did some reading in the service manual and it says things to check:

a.) low idle fuel mixture is improperly adjusted-adjust low idle fuel needle
b.) float level is too low
c.) idle holes plugged; dirt in fuel delivery channels. remove low idle fuel adjusting needle. clean main fuel jet and passages, blow with compressed air.

I think I will check this tomorrow and see what happens.
 
  #3  
Old 12-13-09, 04:28 PM
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Still having problems. I checked the low idle fuel mixture and adjusted it and cleaned it to no avail. I have not checked the float as I have a question. Will the gasket need to be replaced on the carb when I take the top half off to check the float?
 
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Old 12-13-09, 04:49 PM
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The gasket will probably come off without damage. The skip may be hard to trace though. It could be a carb problem as you suspect. Since the removal of the plug wires makes it worse on each side, then I would rule out ignition and suspect carb/fuel problems.
 
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Old 12-13-09, 04:53 PM
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Originally Posted by cheese View Post
The gasket will probably come off without damage. The skip may be hard to trace though. It could be a carb problem as you suspect. Since the removal of the plug wires makes it worse on each side, then I would rule out ignition and suspect carb/fuel problems.
Since I have an extra, just bought a replacement for another machine, I may pull the carb off that one and see what it does.
 
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Old 12-14-09, 02:46 PM
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Pulled carb today and put the backup on, still have the mis. Between this one and the other I am about to pull my hair out. I even sprayed some WD40 around base of carb to see if possibly the gasket was at fault, still no change. To me the plugs look like they are lean, or it is a timing issue where the timing may be advancing itself too much. Any more ideas? I am getting ready to throw in the towel and take it to a small engine guy, but I can't stand being beat on these things.
 
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Old 12-14-09, 06:08 PM
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Is the fuel pump delivering sufficient flow?
 
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Old 12-14-09, 06:42 PM
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Replaced that too. Checked presure, 4.5 psi at carb. Forgot to mention that. Is that sufficient on these small engines? I run 7 psi on my race car, but not exactly the same application.
 
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Old 12-15-09, 09:34 PM
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May have found my problem. After further inspection today I noticed one of the intake gaskets was leaking pretty bad. Called the distributor warehouse said they had the gaskets. Drove 45 minutes to pick them up, get there at 5PM. Drive 45 back to the shop and wouldn't you know it...the wrong @#$%^*% gaskets. Just my luck, but hopefully this will correct the problem. Will find out tomorrow.
 
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Old 12-16-09, 03:32 PM
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Fixed...intake gasket. Running like a charm now....music to my ears.
 
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