Kohler command driving me CRAZY!

Discussion in 'Mechanic and Repair' started by shopteacher, May 12, 2009.

  1. shopteacher

    shopteacher LawnSite Member
    Messages: 60

    Alright fellow gearheads
    I have a 15 horse Kohler command model cv15s. It was not running very smooth so I did a leak down test. The only air escaping was out the dip stick tube. I did a compression check and I had 120 pounds. I did not expect this much compression.

    The next logical step was installing a carb off a good running engine and it still ran poor. After all, the original carb may have something wrong with it, even after cleaning it.

    I figured the head needed to come off, and sure enough it was leaking even with 120 lbs of compression.
    The cylinder wall looked very good, with no scratches except for the crosshatching. That eliminated the possibility of a broken ring.
    After cleaning the carb again and installing a new head gasket, I started it up and it still ran very poorly!!!!!!

    SOOOOOOOOOOO, I took another head of off another engine that was known to run good. Still ran bad.

    I even tried switching the known good coil, still ran poorly
    I even tried changing the oil figuring maybe the hydraulic valves were sticking or something. STILL RAN BAD!!!!!!!!

    Its backfiring a little and sputtering while it runs

    What the heck is the deal??????????????
    The only thing left is that maybe the hydraulic lifters are bad??
    I am at my wits end on this one
    Any suggestions?
  2. AmsoilPower

    AmsoilPower LawnSite Senior Member
    Messages: 938

    Have you checked the flywheel key? Rarely happens on these, but.......... if it is backfiring, it could be timing related.
  3. davidl79

    davidl79 LawnSite Member
    Messages: 79

    do you have a clear fuel filter on it? If so I would also check to see if you are getting enough fuel.
  4. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Yeh it's usually something simple but even if it isn't, tearing into the engine is the absolute last thing to do :p

    I would go ahead and swap the spark plug and air filter,
    and how about the rubber PCV breather tube?
    If that's cracked or leaking air it can make it run like crap.

    Also is the replacement coil properly gapped?
  5. shopteacher

    shopteacher LawnSite Member
    Messages: 60

    Thanks for the replies
    The flywheel key is good, and the breather tube is good. Its also getting plenty of fuel.
    What about the lifters?
  6. freddyc

    freddyc LawnSite Senior Member
    Messages: 578

    does that engine have the auto compression release on it?

    If its backfiring the timing might be off.

    Any more clues such as

    1/ it runs poor cold or hot. Or under load?

    2/ condition of spark plug--- wet, oily???

    3/ air fuel mixture?

    I'm not familiar with that model but I'd be checking all ignition settings. It makes a difference to know when its running bad and if it has power---- compression is not likely your problem. Standard things like air mixture are more probable.
  7. viper00085

    viper00085 LawnSite Member
    from NC/VA
    Messages: 237

    With such a high compression reading I would check the cam/valve lifts out. I have seen quite a few soft cam lobes on CV15's built from 3-6 years ago. The lobes (usually exhaust) will wear down and only open the valves a little bit causing low power/loss of exh flow and possible compression release isues, hence a lot of compression.

    Lifters could be bad, sticking, etc. At 7-10 bucks a peice, may be worth just sticking two in there if you dont see any visible cam lobe issues.

    Also if this a CV style engine were you have to set the lash, make sure you are pushing down on the push rod side of the rocker arm to bottom out the hydraulic lifter as much as possible, then adjust/set the lash. Other wise once your lifters bleed down,etc your lashes will prolly be way off and to large.

    To me, something on there is causing to much compression. Usually the CV 12-18's ring in at 60-90pounds as they have a pretty big compression release designed into them. I would be looking down the road of cam lobe issues, lifters or lash settings (if adjustable) since you have done a lot of checking in other areas already. Good luck with it and keep us updated on what you find.

    ** also something, just to check. Check that plastic insulator block behind the carb for air leaks and cracks. Remove and inspect it or spray some carb clean on /around it while running and see if the engines changes tune at all indicating its sucking the spray in (air leak). Could be a source of a major lean condition?
    Last edited: May 12, 2009
  8. shopteacher

    shopteacher LawnSite Member
    Messages: 60

    I replaced the lifters (they were hard) with known good ones, which were soft.
    It still ran poor.
    This is a matter of pride now. I have to find out why this doesn't run right.

    Any other thoughts?
    I will look at the cam lobes, but could it be a broken ring? There is no scratches in the cyllinder,
    as a matter of fact the cylinder walls look real good.
  9. shopteacher

    shopteacher LawnSite Member
    Messages: 60

    I dissassembed the engine and found no problems that I can see. This is very baffling.
    Any other thoughts?
  10. Den69RS96

    Den69RS96 LawnSite Member
    Messages: 96

    Bad cam maybe? Are the valves getting hung up? Valve springs check out ok?

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