Follow up on oil blow by

Discussion in 'Mechanic and Repair' started by jlslavey, Jul 30, 2007.

  1. jlslavey

    jlslavey LawnSite Member
    Messages: 9

    Had oil coming into carb and out of breather plate. Since then I've pulled heads, valves did not look like they were stuck open, other than the normal build up due to 900 hours, head gasket did not looked blown ( thought not sure if one can look and tell, but no cracks in it) question now is before I start putting back together is there a way to check the rear and front seals to see if they might be sucking air into crankcase? Trying to fix my problem with oil blowing into carb. Any other things I might look at while I got it apart?
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I just went back and read all your post, Since you now have this engine tore down and you felt air coming from the carb with air applied to the cylinder I would suggest lapping the valves and see what the seats look like and check the guides for wear. Also replace the valve seals since you will be right there.

    In some cases you can't look at one of these head gaskets and tell if it is blown or not, Nor can you look at a breather reed and tell whether it's weak or not. The reed is made of a type spring steel and can weaken and eventually break in half, For a couple bux replace it.

    While you have the reed out check for any burrs, Casting marks etc. around the hole in the block mating surface.

    When you start to re-assemble follow the instruction sheet that comes in the head gasket kit.

    Good Luck
  3. John Stiles

    John Stiles LawnSite Member
    Messages: 42

    I had a mower brought to me that used nearly all the oil during just 1 mowing of about 1/4 acre! There was evidence of oil in the upper reaches of the carbuerator and inside the air cleaner. I decided that the air cleaner was completely blocked, and the motor was trying to breathe through the crank case. Replaced the air filter, and the problem abated. This may or may not be your problem, but it is a consideration for everybody! ~john
  4. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    This post brought to mind;
    If a baffle is broke loose inside the muffler it could restrict exhaust flow thus build excessive pressure in the crankcase also. I have seen this a few times, Just something else to check into.

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