Motor / Oil Pump building up too much pressure, blowing the cap off my oil bag.

Discussion in 'Engine, Fuel and Exhaust' started by Greg K. Johnson, Aug 5, 2012.

  1. Greg K. Johnson

    Greg K. Johnson New Member

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    I have a custom hard tail that I have ridden since 1998 when it was built. It has a 96” S&S Evo that has started building up so much pressure that it has blown the oil cap off twice and drenched the rear end of the bike as well as my own with scalding oil. The bike was out of service for about a year for some minor issues not related to the oiling system. I put it in a shop because it needed a carburetor kit which I have never done and a few other things. When I got it back it blew the cap on the way home. Does anyone have an idea why this has happened, it never has in the past.
     
  2. 89stroker

    89stroker Active Member

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    Can you elaborate what else was done to the bike when it was in the shop? It may give the board some more info to go on.
    Sounds like crankcase breather not allowing excess crankcase pressure to be released. Not sure what that S&S has for crankcase breathers, do you know if they feed back into the carb? If so, was any air breather work done at the shop?
     
  3. Greg K. Johnson

    Greg K. Johnson New Member

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    Well the shop is actually owned by my sister-in-law’s ex-husband, so it’s kind of like extended family. He mainly works on cars, but he has had many different makes of motorcycles over the years. I think he really just did the carburetor kit and checked my starter because it was dragging pretty slowly. After the first time it did it on the way home from the shop I called him and ask if he may have caused it. He said he didn’t mess with anything like that. Now that you mention the crank case breather I remember that several years ago I installed the S&S breather assembly that attaches to the bracket of the air breather. He may have messed with it not knowing when he did the carburetor kit.
     
  4. lordharold

    lordharold Active Member

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    could he have added oil to the bike.maybe had checked it and found it low from setting for a year and the oil possibly draining back into the engine
     
  5. blademan

    blademan Active Member

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    My thought exactly, in fact I would bet on it.
     
  6. BUBBIE

    BUBBIE Well-Known Member

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    ***********************
    lordharold has something here... and blademan

    May I add:

    Too much oil added ADDED when NOT checked properly,,,,,, will blow the plug every time. OR a seal.

    OIL Draining into the motor Sump;

    Bikes with top-side oil bags Must be checked for the proper level AFTER a very short idle (2 minutes max) (but confirmed First, that enough oil is there to start) after they have set for a length of time. some do this over night.


    That cold check, THEN will get you out and about safely.

    Check when you get back in while HOT for the proper amount...

    My 06 sport 1200 R leaks/bypasses a Good amount into the Sump area in a couple of days and Nothing shows on the stick BUT I Can see the Needed amount of oil in the lower part of the tank..

    I never Blip the throttle while the RE-pumping into the oil tank is doing it's thing... Problems can happen IF you do try to move things along too fast.

    2 minutes,,,,, all the excess sump oil should be back into the oil tank and back to normal.

    signed....BUBBIE
     
  7. Jennmarr

    Jennmarr Junior Member

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    If the oil tank was overfilled because of a leaking check valve it will blow the cap almost immediately on start up. There is no way it would take long enough for the oil to heat up to "scalding" levels. I think a venting issue is the more likely cause here.
     
  8. lordharold

    lordharold Active Member

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    I have also seen the wrong filter cause this. Such as maybe a twin cam filter on an evo
     
  9. Greg K. Johnson

    Greg K. Johnson New Member

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    I tend to agree; when I upgraded the venting system several years ago I removed the breather that attaches to the crank case. That’s a quick easy way to trouble shoot it by putting one back on. I will try that the first day it’s not 105 degrees. Thank everyone for the input and support.