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Thread: oil tank vent

  1. #1
    Join Date
    Oct 2002
    129 greenwood circle milford pa 18337

    Default oil tank vent

    I have a 48 and 47 chief, I built them both not to leak oil and they don't, except what comes out of the oil tank vent . After a ride and I park them the vent drips out about a tablespoon of oil over time. Is this normal? should I pinch the tube a little ? any suggestions,thanks

  2. #2


    Because oil return blows out some crankcase vapor with returned oil I say it is normal. Watch the return line while running and hot with oil cap off and you'll see the vapor with oil returned. If it is more than a vent tube amount then oil tank would be overfull leaning over on kickstand. Vents drippings don't count as oil leaks so you did good.

  3. #3
    Join Date
    Apr 2008
    Oak View, CA.


    I used to have a bad habit of over filling my oil tank. Maybe because I would check the level too soon, before the return pump sent the slightly-by too full sump back into the tank. Maybe because the vent tube wasn't sticking up above the oil level, when on the side stand. I solved the problem with 2 remedies... one, I made sure the vent tube (inside the tank) was well above the oil level (when the tank is full, on the side stand)... and two, the better idea... was to make a "dip stick" by cutting up a soup can, a strip about a half inch wide and 3 inches long, bent a tab about 1/2", and J-B welded it to the underside of the oil tank cap. I also run a KIWI oil filter in the tank, so I was careful to be sure the 3 inch tab didn't twist all out of shape when I tightened the oil cap. I then marked with a punch, a full mark, a half quart useage mark, and a 1 quart useage mark. Now I know exactly how much oil is consumed. Just be sure when you J-B the tab, you clean the inside of the cap with thinner or something to remove all traces of oil so the epoxy will stick when cured.
    I've had the "dip stick" on the oil cap for more than 6 years... wondered for the first few months if it was going to fall off, but it seems to be working fine. The first one I made was with an old feeler gauge, but it was too stiff, hit the oil filter, so I thought a softer piece of tin would work better. The soup can, I found in the dumpster, seemed to be a much better choice.
    No more leaks from the pesky oil tank vent tube. Don't pinch the oil tank vent tube !! Don't overfill the oil tank. Keep the level in the oil tank below the vent tube opening inside the tank.

  4. #4
    Join Date
    Sep 2012
    Saltsburg PA


    Seems pretty normal from what I have seen. Mine has always done it and I tire of explaining to the HD guys its supposed to do that and not an actual leak like their bikes have. It takes maybe 15-20 minutes to start dripping after engine is shut off and will continue a slow drain for several hours. As ChiefTwoKicks states the fuller my tank is the more it will drip. I have also noticed if I'm running higher speeds in hot weather it will drip more. Mine will eventually quit if I let the level drop to a little more than half full but I don't like to run it that low especially when hot as it also provides cooling.
    Agree do not pinch tube to try and minimize
    Jason Z
    AMCA #21594
    Near Pittsburgh PA (Farm Country)
    Allegheny Mountain Chapter

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