20 hp kohler trouble

Discussion in 'Mechanic and Repair' started by buzzer12, Jun 2, 2007.

  1. buzzer12

    buzzer12 LawnSite Member
    Messages: 10

    could someone please help me!! i'm asking again. i put new rings in, put it back together, new head gaskets. here's the problem i'm getting, one of the lifters is bending. plus when it does fire, i can see in coming out of one of the eshust port oil .plus i can actully see the fire inside the head, now when it does start, when i put the muffer back on, it won't start, take it off it will????????????? now when i put evrthing back i did it by the book . do i need a new head or should i just buy a new engin???? any help would be great thankssssssss
  2. tomo

    tomo LawnSite Senior Member
    Messages: 660

    1/a lifter bending very strange ,are u reffering to the pushrod ?????????

    soak lifters over night in light weight oil
    are the lifters worn on the base where the cam operates ,any depression in this area even minor replace lifter .Cam also becomes suspect when lifters r doing this [soft lobes ,very common in OEM cams]

    were the heads serviced b4 reassembly [carbon etc can cause valves to stick and place greater than normal load on valve train ]

    Camshaft to crankshaft timing ,marks aligned ??????????

    Muffler causing engine not to run ,very unusal unless completely blocked u would think .

    Engine bores measured properly taper and ovality ???????
    Engine bores ,were they honed only or bored as well?????????
    What was the cross hatch angle of the hone pattern ??????
    Does the engine have nickle seal bores or cast iron ????

    tomo ,any Q :waving: :waving:
  3. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    With the muffler off you will see fire in the exhaust port. You either have a binding valve or the mechanical timing is way out to bend a pushrod. How many times has it bent a pushrod? Once you get ll that fixed make sure the flywheel key is not sheered. Don't buy a new engine - I think we can help you.
  4. buzzer12

    buzzer12 LawnSite Member
    Messages: 10

    the push rod bends every time i will check the flywheel i made sure the timing marks lined up when i put it back together please i would like some kind of guidinance to get this running pleeeeeeeeeeeeease
  5. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    The flywheel key will not make the pushrods bend. I just wanted you to check it after you have the mechanical problems fixed. I think your cam timing is off and your valves are hitting the piston.
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Did you start the engine immediately after installing the push-rod ?

    When the lifter is pumped up it's hard as a rock and when you torque the rockers down all your doing is opening the valve. If you start the engine in this state the piston will smack the valve bending the push-rod. Best to let the engine sit for 20/30 minutes to give the lifter a chance to bleed down before trying to start it up.

    Also, Can you put your thumb on the end of the rocker and push the valve down ? This will tell if you have a stuck valve.
  7. buzzer12

    buzzer12 LawnSite Member
    Messages: 10

    i took the engine completly apart , stated all over again , the engine now starts , and does not bend the push rod . but as before when i attach the muffler it will not start take the muffler off and it starts . i do notice that there is alot off back pressure in the crankcase as i said before i put rings in this engine . aqnd a new carb and muffler. is the compression getting by the rings??? i put new gaskets in too!! while running if i take out the dipstick it almost pops out due to the pressure in the crank case . any idea whats causing this thanks for your help...........
  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    It's time to post both model and spec. numbers off this thing.
  9. petez

    petez LawnSite Member
    Messages: 9

    When you say the lifter bends, do you mean the valve? or the pushrod from the cam to the valve? Either way it should not bend and if it was bent it did not fix itself. If you see a flame coming out the exhaust port that valve is not closing, if it runs without a muffler but with muffler on it does not run. Elimination will tell you that you have a problem with the exhaust. It's not the muffler, that leaves the exhaust valve. The lifter you said bent wouldn't happen to be the exhaust one would it? Your problem lies in the exhaust valve. take the head off and see if the valve is seated, check that the spring for that valve is not broken. If you have a valve cover that you can take off and see the valves, turn the motor over by hand with no spark plug and watch the valve movement make sure the valve completly seats then do it with the muffler on and see if it still seats. If no problems seen then push on the valve with force and see if you can compress the spring it should be extremely difficult if you can even move them, if you can depress it, that valve spring is probably shot. It should take probably 60 lbs of pressure to depress one.
  10. buzzer12

    buzzer12 LawnSite Member
    Messages: 10

    here are the spec's skh624u1g2ra mod. ch20s. spec, 64554, dis 624
    ser# 2922306151 like i said the push rod does not bend any more . it does start right up without the muffler . i will check the valves today, and it was the exhust valve that was bending. there is a whole lot of back pressure in the crankcase thanks everyone for ur replies, it seems the back pressure is my only promblem now!!

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