Rebuild or Re-power?

Discussion in 'Mechanic and Repair' started by columbiaplower, Mar 25, 2008.

  1. columbiaplower

    columbiaplower LawnSite Senior Member
    Posts: 462

    Just bought a bobcat 60in walk behind with a 20hp kohler engine on it. Starts good but in thick grass it bogs down. Any ideas? Got the mower for cheap so if it needs a new motor its not the end of the world. But i was thinking if it just needs a valve job i could try that first. Any ideas would help
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Make sure it's running on both cylinders (Coils working).

    Loosen both plug boots for easy removal, Start the engine and let idle. Remove each plug wire one at a time with rubber handled pliers etc. and see if it shuts down when one is removed. If it does the one you just removed is good and the other is bad.

    If/when you reply with the results post the engine model and spec numbers.
  3. columbiaplower

    columbiaplower LawnSite Senior Member
    Posts: 462

    yea that was the first thing i checked seems to be running on both. Tomorrow when Im at my shop, Ill get more info on the engine model.
  4. columbiaplower

    columbiaplower LawnSite Senior Member
    Posts: 462

    well i took the valve covers off and im pretty sure i need head gaskets

    the engine is a CV20s spec 65514
  5. columbiaplower

    columbiaplower LawnSite Senior Member
    Posts: 462

    anyone know the j thomas part numbers for the head gaskets?
  6. mowermankevin

    mowermankevin LawnSite Senior Member
    Posts: 270

    Just curious,how do you know it needs head gaskets by pulling the valve covers? Have you tried a compression tester on each cylinder, or bad leakage around head to cylinder fit? Before you make a expensive teardown have some other folks you trust come over and get some ideas and buy a pizza and brew,(on you) and get concensus, then you can blame it on them, and not kick yourself if it's not any of what you thought it was,it's amazing what solutions come from running it by other opinions.
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    I agree with Kevin,

    How thick/tall is the grass ?

    What does the spark plugs look like ?

    Have you tried new plugs ?

    What is the no load RPM set at ?

    Have you checked the governor for proper adjustment ?

    There are things that can cause this without being a blown head gasket, A compression/leak-down test would show a blown gasket.
  8. sawman65

    sawman65 LawnSite Senior Member
    Posts: 751

    compression test mean next to nothing on a kohler. you need to have a leakdown test done and you will know beyond a doubt what is wrong with that engine
  9. columbiaplower

    columbiaplower LawnSite Senior Member
    Posts: 462

    Plugs have been replaced the day i bought it. There is oil leaking out from around where the cylinder meets the head. Theres also oil blow by in the air intake. The night i bought it we did the pizza and beer thing and we all kinda agreed that it needed head gaskets, intake gaskets and exhaust gasket. When the right side valve cover is removed and you turn the engine a little you can hear the hiss of a leak. DId the compression test but no leak down, will have to do that to confirm the compression test.
  10. caseymax

    caseymax LawnSite Member
    Posts: 16

    Hi If the head gasket is leaking oil it needs to be removed, if the valve cover is blowing oil also you have return holes in the bottom of the head that may be plugged but that wouldn't’t make your head gasket leak, it has a reed plate in the head by the lifters to relive the presser, make sure it is seating good. If your intake gasket is blown on that side there is a good possibility that you have blow by on that piston. Scored pistons on Koler are not uncommon due to over heating from-- cooling fins being filled with grass or hot spots from wrong plugs and bad gas, so forth. You can look at your cylinder walls when you take the head off and kind of tell the shape of the piston and rings. A simple compression test is a good indicator of the condition of the piston, leak down is ok if you can’t pin point the problem easily. The head gasket comes with new head bolts, if it had studs instead of head bolts you need to remove them and use the new bolts that came with the head bolts. The head gasket is the same for all Koler 17 thru 23 hp. The torque on the head bolts is very important on reassembly. You can rebuild for like $200 (new pistons and rings and gasket kit) if you think the condition of the block is worth it. If you do make sure you don’t use an oil pan gasket on this engine, use RTV black gasket maker.

    Monrovia In

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