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Latest post Mon, Mar 5 2018 9:57 AM by sfranta. 3 replies.
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  • Sat, Mar 3 2018 4:31 PM

    • 3krazy
    • Not Ranked
    • Joined on Sat, Mar 3 2018
    • Posts 1

    Excessive crankcase pressure

    Hoping for some help. I have a 1990 Softail Custom that had to replace the cylinder base gaskets on. I was able to leave the Pistons in the bores and just pulled the clips on the connecting rods. I basically replace all the top end gaskets with Cometic gaskets and put it back together. It runs great with no leaks but after running a while it will puke oil out of the crankcase breather just like it does if it has been sitting too long. I have never had this happen before when it was warm. It doesn't smoke from the pipes at all and has about 23,000 miles on it.

  • Sat, Mar 3 2018 5:55 PM In reply to

    • FX
    • Top 10 Contributor
    • Joined on Sun, Mar 12 2006
    • Tonawanda NY
    • Posts 5,201
    • Moderator

    Re: Excessive crankcase pressure

    Always look to the last thing you did before the problem started... I know you're not going to want to hear this, but...It may be that the oil return holes in new gaskets are not there (wrong gasket), or not aligned correctly with holes in heads/cyls/crankcase...

    If that engine has the umbrella valves for the breather system, I would check them first...


    Don't force it, get a bigger hammer.

  • Sun, Mar 4 2018 6:26 PM In reply to

    • Ironhead
    • Top 10 Contributor
    • Joined on Tue, Mar 21 2006
    • Near Sunset at Sunset Beach, O'ahu, HI Oct 23, 15
    • Posts 2,653
    • Moderator

    Re: Excessive crankcase pressure

    3krazy - first welcome to the forums - what part of the country are you from?

    Other than what Fx said, the biggest reason for excessive crankcase pressure is compression slipping past the rings - since you were in there disturbing all that stuff, it wouldn't hurt to take a few minutes and do a peak compression and a compression leak down test.

    hope this helps

    The first tool out of the box should be the "book"  Geeked

  • Mon, Mar 5 2018 9:57 AM In reply to

    Re: Excessive crankcase pressure

     did the base gaskets come right off, or did you have to scrape them off? if you scraped, did you have the bore holes in the case plugged with clean shop towels to keep gasket materiel from getting into the engine? if any gasket materiel got loose in the engine, it may have plugged an oil passage somewhere, or restricted the vent or return line to the oil tank.


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