Kohler CH20S Command not running right.

Discussion in 'Mechanic and Repair' started by Impressions Landscaping, Nov 7, 2012.

  1. Impressions Landscaping

    Impressions Landscaping LawnSite Member
    Posts: 215

    Hi, I have a Kohler 20 horse motor on a Walker mower that won't idle at all and doesn't have much power at all. I rebuilt the carb with the few new parts that come in a rebuild kit for these. The only way to get it to run somewhat smooth is to run with the choke 1/2 - 3/4 closed. There's not much going on inside the carb of this machine and its been blown out, cleaned with carb cleaner, soaked, blown out again and still runs like crap. Any ideas on what to try next before I spend $380 on a new carb? Also this motor has no accelerator pump built into it. And the motor is probably a 2000 or so.
     
  2. ericg

    ericg LawnSite Silver Member
    Posts: 2,559

    Those carbs have many small orifices so a soak may not be the best way to clean them. We use an ultrasonic cleaning machine and it works wonders on those carbs. By you closing off the choke you are causing a surge in vacuum and that may be enough to draw the gas up the tube within the carb especially if the tube is partially blocked.The other thing is, have you checked for any vacuum leaks at the base of the carb? If there is a vacuum leak, closing the choke allows the leak to provide enogh air to make it run good. Start the engine, run it with the closed choke and spray carb cleaner around the base of the carb. If the engine increases rpm's that is your vacuum leak since the carb cleaner is adding extra fuel to the mix.

    Eric
     
  3. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    I'm thinking sucked in intake gaskets....pretty common issue..
     
  4. Impressions Landscaping

    Impressions Landscaping LawnSite Member
    Posts: 215

    Both of you guys, thank you for your response, I'm going to go out and try that in a few minutes and see what happens. If either of those don't fix it, what else should I do??
     
  5. Impressions Landscaping

    Impressions Landscaping LawnSite Member
    Posts: 215

    What are the chances of the float needing to be adjusted a little bit?? Tried carb cleaning around all the areas where there's a possibility of a gasket being broken or blown, no issues there. If the mower has a load on it it runs down on power, but smoothly, not like it's a misfire or anything like that. It runs down like its running out of fuel. As soon as you ease up and either slow the mower down or shut down the blades, the RPM's pick right back up again. If thats the case then it should be a simple adjustment. Just trying to get some ideas.
     
  6. ericg

    ericg LawnSite Silver Member
    Posts: 2,559

    How many hours are on the engine? Just for curiosity, have you done a compression test or a leakdown test?
     
  7. ericg

    ericg LawnSite Silver Member
    Posts: 2,559

  8. Impressions Landscaping

    Impressions Landscaping LawnSite Member
    Posts: 215

    Funny you ask about the compression test. I did one tonight, since the motor has around 1700 hours on it. The front cylinder has around 90 PSI and the rear has around 140 PSI. The front plug has burnt up oil on it, so I cleaned that, and also checked the rear plug which was fine. Obviously the motor needs a ring job. The carb is still screwed up however, since cleaning the plug did nothing to fix the issue with the idle. Unless you think otherwise.
     
  9. ericg

    ericg LawnSite Silver Member
    Posts: 2,559

    You should do a leak down test to verify if it is rings or valves just so you know what you are up against. As for the carb, I still think that the main jet and or the internal of the carb is partially blocked.
     
  10. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Im surprised it ran this long...optimum compression is 180 psi...
    130 to 150 will run somewhat ok...as long as there is not more than 10 psi difference between the cylinders..
    With 50 psi difference...and the low side at 90...you have a bad valve or a blown head gaske that sounds like air brakes when you turn the engine off.
    The wait is over...pull the head...
     

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