The Cause of a Smoking Engine

Discussion in 'Mechanic and Repair' started by Mack77, Oct 26, 2009.

  1. Mack77

    Mack77 LawnSite Member
    from NJ
    Messages: 208

    Hi Guys,

    One of my machines (23HP Kawasaki) with about 1500 hours recently just started to smoke (burn oil). It smokes a lot when I first start it, then less and less until there is no smoke at all and it seems to run normally. The smoke lasts for a few minutes then dissipates.

    A few questions:

    1. What causes this?
    2. Is it cost effective to repair or replace an engine like this?
    3. What will happen if the engine continues to run, while burning oil/smoking?

  2. Sharpcut 1

    Sharpcut 1 LawnSite Senior Member
    Messages: 452

    Probably bad oil seals. When the engine sits, there is oil in the valvecovers. When started, the oil is drawn into the cylinder till it's burned off. When it's running, oil is going back in the drainback hole.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    That would be valve stem seals just to clarify, If you happen to go that far check for excessive side to side movement in the valves/guides......
  4. mdlwn1

    mdlwn1 LawnSite Silver Member
    Messages: 2,443

    Would this explain my older single cylinder Kawi's that would SOMETIMES Smoke heavily at startup..20-40 seconds and most of the time not?
  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Possibly, But I've seen condensation build-up in the crankcase cause the same thing when left sitting overnight.
  6. long71

    long71 LawnSite Member
    Messages: 3

    I have a similiar problem with my Kawasaki engine, but all of a sudden along with the smoking, I had a great loss in power. Enough to run, but not enough to engage the mower deck effectively. I checked my compression. It was fine in one cylinder, but I have no compression in one cylinder. The piston is moving. Someone suggested I have a valve stuck open. Does this sound about right? What's the easiest solution. I have read about lapping the vales, but would it be easier to replace the valves and seals?
  7. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Messages: 850

    Could also be the rings here.
  8. dKoester

    dKoester LawnSite Gold Member
    Messages: 3,298

    Do you ever adjust your pushrods. My standers have to be adjusted around every 300 hours.
  9. long71

    long71 LawnSite Member
    Messages: 3

    Thanks, I guess I won't know for sure until I dig into it. I had replaced the head gasket about a year ago on this cylinder and the valves did show some build up, so I am hoping that it is a valve problem vs rings. I am just trying to get a few more uses out of it this year for mulching leaves, I can give it a good overhaul this winter.
  10. long71

    long71 LawnSite Member
    Messages: 3

    Update to above.... I pulled off the valve cover and noticed that the push rod to the intake valve was not connected. I pulled it out and it was bent pretty good. I pushed down the exhaust valve and it moved frrely, but when I pushed on the intake valve it would not move until I tapped on it. I put a new pushrod in and ran it again. No difference, so I took it apart again. Same thing, bent push rod. So, I pulled the cylinder head off and noticed a good amount of build up on the valves and the head. I assume the push rod is bending because it cannot open the intake valve due to build-up. Is there anything else that would cause the bending. So I am hoping once I clean up the valves and head, it should fix the problem. Thoughts??

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