25hp Kohler Command carb setting?

Discussion in 'Mechanic and Repair' started by KathysLGC, Apr 2, 2005.

  1. KathysLGC

    KathysLGC LawnSite Bronze Member
    Messages: 1,345

    I got a used Lazer Z and the RPMS where low and the engine just wasn't running right. I did a well needed tune up and rebuilt the carb. Upon re-installation of the throttle cable I noticed at full throttle the butterfly valve isn't open all the way. I usually adjust the throttle cables so at full the valve is fully open but with this engine thats not the case. I put a tach on it to see the rpms and I adjusted the idle to 1500 rpms (after warm up), I adjusted the low needle (i replaced the old one) and at full throttle I was only getting 3400 rpms with no load.
    I adjusted the governor up a notch but it didn't do much. If I pull the linkage on the carb I can get the rpms up but the linkages where the throttle cable attaches to are at max. Any idea how to get this engine to purr as it's supposed to? Does the butterfly valve on the carb not open fully at full throttle? The Model engine is CH25. I'm going to print out the service manual tomorrow when I get to work but wanted to get your input on this.
  2. npilcher

    npilcher LawnSite Member
    Messages: 27

    the butterfly valve does not open all the way on this engine or the cv series of kohler. If it did, when you throw your throttle wide open the engine would "run away" and damage. Thus by not being open all the way you achieve the correct high rpm's @ 3600 and when the governor sinces any strain it can throw the valve open further to compensate.
    Try moving your governor spring up or down a notch. If that does not work look where the cable attaches to the carb arm and there may a metal stop tab that can be bent a little for extra cable pull.
    I set all my governor springs so that at full throttle and no load you can detect a SLIGHT surging in the engine that levels off after a couple of seconds. This ensures a very sensative governor and alot less engine strain. Does not in any way harm the engine and makes a TON of difference in thick grass mowing.
  3. KathysLGC

    KathysLGC LawnSite Bronze Member
    Messages: 1,345

    Hmmmm. I hate this linkage design. I did notice the carb has a fixed main jet. I rebuilt the carb and replaced the low jet. I didn't even attempt to look at the main jet. I flushed the carb out in the rebuild and every is spotless. The engine starts right up now at lower rpms then when i first got it. After adjusting the low needle and idle stop, the engine runs smoother but i just can't get the rpms up. Normally I'll set the rpms to 3750 at idle so with blades engaged I get 3600rpms. Currently with blades engaged i get about 3300rpms. Thats way to low. A slight pull on a linkage and i'm right where i want it to be I just can't get it to stay that way. I did notice when i pull on a linkage to get the rpms up (36-3700) I feel the linkage pulling in the opposite direction as if a spring or setting is keeping it from staying. i just need to find out which spring/lever/clip to adjust...

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