30hp Kohler Rebuild

Discussion in 'Mechanic and Repair' started by LewisL230, Dec 5, 2012.

  1. LewisL230

    LewisL230 LawnSite Member
    Messages: 39

    Well my season is over so it's time to tear down. The motor is a ch750 30hp Kohler on a 2006 exmark. It has about 1600 hrs on it. I bought it from another LCO. It had been sitting a while and when I got it it ran great, with just normal tune up. Well after last winter the problems started. At this point it uses a quart of oil ever 1.5 to 2 hours of running. It hasn't been that bad until recently so I decided to limp it the last month instead of trying to do a big rebuild during the season. So here I am. I plan to pull the motor off and put new rings, new valve seals, new reed valve, new governor shaft seal, and new gaskets and filters. My question is is there anything else I need to do while its apart. Should I get the valves and seats surfaced? Should I run a hone through the cylinders or leave them be? Just looking for some experienced advice. I've built v8's my whole life but need anything this small.
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  2. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,190

    Absolutely get the heads/valves done!
    You should go to the Kohler website and download a free service manual.

    I always use a brush type hone to deglaze/condition the bore. But you also need to check for excessive wear.
    If you've done v-8s etc, then you know what ya gotta do.
    Get the service manual.
  3. Oldtimer

    Oldtimer LawnSite Bronze Member
    Messages: 1,459

    I am assuming the engine is not blowing white smoke, just consuming oil.

    Before you do anything, check the crankcase vacuum. The gauge has a cone shaped tip that goes into the dip stick tube. You should see a -10 psi. If he needle bounces back and forth the problem is head gaskets.

    Replace the head gaskets and head bolts.

  4. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    Normal crankcase vacuum on a Command twin is 2psi...
  5. Oldtimer

    Oldtimer LawnSite Bronze Member
    Messages: 1,459

    Normal crankcase vacuum on a Command twin is 2psi...

    You are right.

    Just a negative needle movement on an analog gauge is indication enough.

  6. Richard Martin

    Richard Martin LawnSite Fanatic
    Messages: 14,699

    Yeah, 1600 hours on a Kohler is just getting good and broken in. I'd definitely look at the head gaskets before a rebuild. If you do a compression test I'd be willing to bet that one side is significantly lower than the other side. Pull both spark plugs and set the throttle wide open. If both sides have about the same compression then do a leak down test.

    Always do diagnostics before you spend a dime in repair.

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