Kohler Command 14 OHV surging and backfiring after cleaning carb

Discussion in 'Mechanic and Repair' started by Beatkat, Apr 28, 2007.

  1. Beatkat

    Beatkat LawnSite Member
    Posts: 8

    :cry: I have a Kohler Command CV14S that was running fine until I used some GumOut carb cleaner on it. It started surging a few minutes after and backfiring (pre detonation maybe?) and now it wont run without the up and down surging/popping. It starts fine, but won't run smoothly as it did before... Could I have fouled the carb? I have checked all the fuel related lines and found one cracked that leads from the fuel bowl to the head, so I repaired that one, checked fuel filter/flow from the tank, but the surging/detonation still remains...I bought this unit used, and ran the engine for a full 10-15 min's while deciding to buy it, it was only after I got it home and changed the oil, plug, and sprayed the carb cleaner in it that these symptoms appeared....the new plug is the same one as orig. equip. and gapped properly (.040).....any help appreciated!...
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Did you have the carb. off and apart ?
     
  3. Beatkat

    Beatkat LawnSite Member
    Posts: 8

    Thanks for the swift reply!...no I have not removed the carb..(and hope I won't have to..)..I bought this lawn tractor with the Kohler...as I said, started the motor at the sellers while debating whether to buy the tractor and it ran fine...got it home and it ran fine...then changed the oil...new plug...ran fine...then a few quick sprays of carb cleaner with the engine at about 3/4 throttle..seemed to bog down a little as usual while burning off the carb cleaner then returned to previous rpm...then shut it off and returned 20 mins. later ...started it up to put it away and the engine no longer ran smoothly...starts right up...no smoke...but won't run at a constant rpm...surging rhythmically up and down and popping occaisionally...really wierd...
     
  4. topsites

    topsites LawnSite Fanatic
    Posts: 21,654

    How's the breather line? I'm talking about this shaped black rubber tube runs from the carb into the valve cover, if that's cracked or badly corroded it could use replacing, might fix the problem. Something about there needs to be a constant vacuum on that breather tube at top rpm or it won't run right.

    On my 15hp vert.shaft it's on the front of the engine...
     
  5. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Start it up and position the throttle where it hunts the most then slowly start applying the choke. If the hunt goes away and it smooths out take the carb. off then tear it down and spray (any brand but Gumout) carb. cleaner through all ports, Passages and jets then re-assemble.
     
  6. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Posts: 910

    If this unit sat over the winter, possibly some water condensed in the tank. While moving it around, a bit of the water on the tank bottom may get in the fuel line and on to the carb bowl, where drops get picked up on a random basis.
    I would try draining the tank and refilling with fresh gas. You may also want to replace the fuel filter with the proper KOHLER filter. Don't substitute.
     
  7. Beatkat

    Beatkat LawnSite Member
    Posts: 8

    Thanks again for the swift replies...This unit did sit (I have no idea how long) and the gas that was in it may be contaminated...it's a good thought...what about Dry Gas....instead of draining the tank, as I just added about 2 gals. fresh fuel? I added fresh gas on the way home from buying the unit, but as I said it was running fine at that point...and I didn't think of the possibility of water in the fuel because it seemed to be running SO well....but it is possible that some water could now be contaminating the fuel....and how does one dispose of 2+ gals. of contaminated gas?? topsites, the breather line was cracked at the connector, and I recut it and re attached....Bill what would be the reason for not replacing the fuel filter with just an ordinary fuel filter? (Briggs, Honda,Husky, whatever)..aren't they all basically the same?...I have replaced several fuel filters in my time and they all appear to be constructed the same way, element wise......I never really thought there was a difference..also is there any way carb cleaner can go bad??... but, as one sprays it through the air cleaner/choke port, isn't it going directly to the combustion chamber and not passing "Go"?...therefore not contaminating the fuel bowl?? or carb jets? ;) As it's Sunday, I may try to drain the fuel bowl and add some DryGas to the fuel, but first I'll try manipulating the choke as Restrorob suggests...I still can't imagine it's anything too serious that would require tearing down the carb...as this thing was running SO well, and appears to have very few hours on it...THAT was the reason I jumped at buying it!!!:realmad:
     
  8. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    Bouncing down the road to your house could have stirred up trash/water in the float bowl and now sucked it into the main jet.

    Not sure what the deal is on the filters, I've been using aftermarkets for years on every thing.
     
  9. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Posts: 910

    "Not sure what the deal is on the filters, I've been using aftermarkets for years on every thing."

    On another tractor forum, there have been a couple instances of Kohlers not starting and/or running poorly with non OEM filters.
    I think it might be a case where a gravity fed engine had a filter for a fuel pump engine installed???
    The filters have different micron ratings.
     
  10. Beatkat

    Beatkat LawnSite Member
    Posts: 8

    Micron ratings only would refer to particle size..not flow rate of fuel..and filters are designed to be passive and not cause any restriction in fuel line flow rate..unless they're clogged of course..the good news is that my situation has apparently been cured..I changed the fuel filter,(to a no name I had lying around) and drained the fuel lines while doing so, added about 3.5 oz. of Isopropyl type Drygas to the tank and agitated the gas, then restarted the engine and after about 60 seconds my symptoms disappeared, and the engine returned to it's surge free operation. I then went out and cut the front and side lawns (about 45mins. worth of mowing) without an issue. I'm guessing that there WAS some water in the fuel bowl/lines/tank and that, coupled with the leaking breather line, caused my problems. You guys called it right and saved me quite a bit of aggravation, and for that I'd like to say a sincere thanks. This is a great forum, and does a lot to bolster my faith, once again, in the Internet's ability to foster human interaction and problem solving.:usflag: :clapping:
    The next question I have is whether I can adjust the top speed of this engine. Is it just a screw adjustment, or is there an electronic governor on this engine. It's kind of hard to see the bottom of the fuel bowl the way this engine is packed in the chassis. It would be nice to have 500 or so more rpm at the top end of the throttle adjustment before the choke kicks in.. Thanks again to all for your support- :drinkup:
     

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