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Choke valve sticking...

Discussion in 'Mechanic and Repair' started by topsites, Nov 6, 2009.

  1. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I've got a Kohler 15hp SP on which the choke valve doesn't always close fully,
    it is so bad that after I remove the air filter and stick my finger in there I can
    feel and hear an audible 'click' as I push it past the sticking point.

    The cable appears to give enough, I've also looked for obstructions and see none...
    Any other ideas?
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Remove the air filter base, Then you can see better. With the choke open grab the butterfly with your thumb and finger and see if it moves around in the slot of the plastic shaft. Also watch for any movement between the shaft and carb body.

    These plastic shafts wear and lets the butterfly hang up in the carb bore, Replace both the shaft and butterfly as a pair.

    Pay CLOSE attention to how the spring is on the shaft so you can re-install it properly, To remove the shaft just grab the butterfly with pliers and pull it out of the slot. I carefully slide the tip of my pocket knife next to the butterfly into the slot to spread it just a little before pulling it out.
  3. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Messages: 850

    It could also be in the linkage to the carburetor from your controls. I had that happen on my Gravely, I had to give it starting fluid from cold start until I figured out that the choke wasn't closing all the way. In my linkage there was an adjustable screw that hits the wire that controls the choke, the screw had loosened itself and wasn't giving enough choke. So before replacing anything make sure your linkages are in proper adjustment. Or like Restro said, your butterfly could be worn/loose. Good Luck
  4. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Thank you!

    Yeah, I've already looked into the linkage and even pushing that by hand
    doesn't always make it close fully...
    Then I've adjusted that throttle to where it pushes harder than it should,
    I even bent it a little and that improved nothing.
    So I don't think the problem lies in the linkage, something is definitely 'catching' it
    and not letting it close, but I appreciate the tip.

    So I will try that bit with the plastic shaft over the weekend, if anything
    goes wrong I have two other 15hp's to look at for reference :)
  5. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I wanted to update this thread as I believe to have found at least the source of the problem...

    The butterfly valve on this particular carburetor appears to be a very close fit to the mouth of the throttle.
    So close in fact, that it was touching one or both sides, and thus catching.

    To make matters worse, the plate has to seat perfectly on the axle which the plate screws on to.
    Two little screws go through the plate, however the holes are a little larger than the screws, so as one tightens these
    I noticed the plate could still be moved from side to side, and up and down.

    After much trying to get it aligned with the tiniest of thumb screw drivers,
    I took it back off and ground down the edges a little with a dremel.

    Now there's a little bit of air all around, and finally it's not catching or sticking.

    Of course I'm still at least somewhat hoping that it really is fixed and the problem didn't lie elsewhere,
    I guess worst case scenario I'll just replace the carb (but what a pita, over a dang choke valve).
    Yes, the engine starts fine now.

    Anyhow, in case it helps someone...
  6. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Messages: 850

    Ya, worst you can do is a new carb. On the Gravely, while mowing the absolute last lawn last year, it just died. Well, the spring loaded choke return piece on the top had busted causing the choke to be stuck closed, and it isn't a replaceable part, it is pressed onto the carb. So that sucked, but I got a good used carb on eBay for $25 shipped. Still running good right now.

    Hope your problems are fixed.

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