25 hp kohler, 1 cylinder running hot

Discussion in 'Mechanic and Repair' started by JHLC, Jul 27, 2005.

  1. JHLC

    JHLC LawnSite Member
    Posts: 147

    Last week while mowing with my 25hp Walker i noticed that one of the two exhaust pipes were glowing red ( I was mowing before the sun came up). I assumed it was a leaking intake manifold gasket that was causing that cylinder to run lean and over heat. I pulled the engine, replaced the gaskets and put the mower back together and still have the same problem. Has anyone ever had this problem before? I'm stumped on this one.
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    I have only ran across this problem once and it's been a few years back,I don't remember the fix though. But I believe I'd start with a compression test or better yet a cylinder leak-down test, That would tell you if its a head gasket leaking or a valve seating problem. It could also be a lifter, Is there any excessive lifter noise ? A good carb. cleaning would eliminate that as being the problem.
    Sorry I can't remember the exact fix ! :(
     
  3. thecrankshaft

    thecrankshaft LawnSite Member
    Posts: 172

    I wonder what muffler you have on there.

    The mufflers that go from 2-1 before entering the muffler can cause excess backpressure/heat for the one cylinder with the longer section of exhaust pipe before the muffler. Kind of hard to explain. The better design is having each of the two exhaust pipes enter the muffler separately.

    What is on yours?
     
  4. thecrankshaft

    thecrankshaft LawnSite Member
    Posts: 172

    Compression tests aren't the greatest because of the ACR (automatic compression release) that opens the exhaust valve during cranking speeds to allow easier pulling/starting.

    Leakdown tests are the way to go with these engines-just make sure that you can hold the flywheel steady so that the air pressure is turning the engine over.
     
  5. Redneckn

    Redneckn LawnSite Senior Member
    Posts: 294

    Leakdown for sure is the way to go.

    I would guess that it is either a blown head gasket or a "lean" type situation. i have seen some mowers that this caused the front grill area to melt and/or catch fire.
     
  6. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Thats why I said leak-down test but not everybody has a leak-down tester in their tool box.
     
  7. thecrankshaft

    thecrankshaft LawnSite Member
    Posts: 172

    Just clarifying for others........

    The compression testers with a hookup for an air hose work nice.
     
  8. Jman

    Jman LawnSite Member
    Posts: 217

    On a Kohler command twin cylinder engine, with a solenoid shift starter, they do not use a compression release camshaft. If it has an inertia drive starter, they will use a compression release cam. If no compression release cam, it is a very true test to use compression. Should be in the 150-180 p.s.i. range.
     
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Your right there, I've had to do that a couple times because my tester was at the shop.
    But still a compression test on a ACR engine my not give a true reading it will show a cylinder imbalance if there is in fact a problem.
     
  10. JHLC

    JHLC LawnSite Member
    Posts: 147

    I will try a leak down test, thanks for the help.
     

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