I was told to turn my Cheetah off at full throttle by my dealer...

Discussion in 'Mechanic and Repair' started by Ijustwantausername, Jun 18, 2012.

  1. Bashby

    Bashby LawnSite Senior Member
    Messages: 445

    My older Kohler backfires when shut down at idle. It doesn't at full or half, If i let it idle then open the throttle as i shut the engine off it prevents the backfiring
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  2. Ijustwantausername

    Ijustwantausername LawnSite Bronze Member
    Messages: 1,728

    Its a 31HP Kawasaki.
  3. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    Idle it down.

    Switch ignition off.

    At that exact time give it throttle.

    You won't increase RPM's by doing this and it will open the throttle blade(s) in the carb.

    Or just buy an EFI. They don't do this.
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  4. VegetiveSteam

    VegetiveSteam LawnSite Senior Member
    Messages: 296

    Do you know if it has a fuel shut off solenoid on the carb? Most do these days. If there is a fuel shut off solenoid on the carb, shut the engine off at full throttle. That should take care of the afterbang. The engine owner's manual it should have shut off instructions in it for both with and without fuel solenoid.

    What the fuel solenoid does is shut off only the high speed circuit of the carb. If you shut the engine off at idle you are still pulling fuel through the idle circuit and that fuel thrown unburned into a hot muffler causes the afterbang.

    When you shut the engine off at full throttle the fuel solenoid shuts off the high speed circuit of the carb but we are still able to pull fuel through the low speed circuit of the carb. This is where the governor comes into play. You have your engine running at full speed. With no load on the engine the throttle is bearly cracked open and the engine is still running mostly off the idle circuit. As soon as you turn off the key the engine starts slowing down. What does a governor do when an engine slows down below what the governor wants the engine to run at? It opens the throttle more. The governor will continue to open the throttle on the carb until it gets the engine back to the RPMs it should be running at. Will it ever get back up to speed? No. The engine is turned off but the governor keeps opening the throttle until it is open all the way. Now we are sucking in a lot of air. The main or high speed jet is closed because of the fuel shut off solenoid. We are still getting a little bit of fuel out of the low speed or idle jet but now there is so much air being pulled in because of the wide open throttle that most of the fuel just evaporates and what makes it to the hot muffler is way too lean to burn. Result? No more afterbang.

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