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Wet Sumping Oil Path, past the checkball

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  • Wet Sumping Oil Path, past the checkball

    Was just thinking about the path oil takes in the case of a wet sump that most everyone sees typically occurring in a bike that sits unused for an extended time.
    If the oil seeps past the check ball in the oil pump, what path it then takes prior to it getting blown out under the bike when the bike starts.

    Does the oil just seep past the tappet blocks/lifters and drain into the gearcase?
    Does it also seep up past the pressure regulating valve, and then out between the pinion shaft/bushing?
    All the way through the pinion shaft, draining out into the crankcase through the rod bearings?

    The gearcase/crankcase gets filled up, and when the bike starts, that oil collected there has to be at a level up over the air/oil separator baffle port and subsequently gets blown out onto the ground until the scavenge gears in the oil pump can catch up and get the rest of the majority of the oil back to the oil tank.

  • #2
    There are three or four paths for oil to enter the motor through the oil pump at rest.
    1) As you say, through the check ball/seat and thence through the tappet blocks into the cam chest, and through the pinion bearing into the flywheel case if it sits long enough. If it's really bad, it will also backflow into the primary.
    2) Often overlooked, a bad oil pump shaft seal will allow oil to go from the feed side to the return side and thence into the cam chest.
    3) On '81 (?) and newer pumps where the excess pressure oil is routed back to the feed side, feed oil will bypass a poorly fit pressure relief valve and into the cam chest. I had an example of a cheap aftermarket pump where this problem was so bad, all the oil would drain from the oil tank overnight.
    4) A bad body or cover gasket can create a leak path.

    Jim
    High Point, NC

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    • #3
      A while back I ran into one that had an aftermarket oil tank with the wrong dipstick. The customer filled it up to the line, but that raised the oil in the tank above the vent or breather line on the left end of the tank so oil would run down that line into the engine bypassing the check ball and oil filter. We even tried a new oil pump before I looked inside the tank with an endoscope and saw what was going on. He would blow out a quart of oil, then the dipstick said it was low, so he'd add another quart of oil and the next day it blew it all out again.

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      • #4
        Originally posted by 77cr237 View Post
        A while back I ran into one that had an aftermarket oil tank with the wrong dipstick. The customer filled it up to the line, but that raised the oil in the tank above the vent or breather line on the left end of the tank so oil would run down that line into the engine bypassing the check ball and oil filter. We even tried a new oil pump before I looked inside the tank with an endoscope and saw what was going on. He would blow out a quart of oil, then the dipstick said it was low, so he'd add another quart of oil and the next day it blew it all out again.
        Sounds like a bad thought process!!!... should always let the engine "talk to ya" ... a dry sump system.. operating properly, will function just fine on a quart or less!!! BTDT

        Jim... I also have heard of sumping into the primary... My Brain just cant wrap around that!!! Can we assume enough oil got into the cam chest that it went to the Primary via the evacuation hose???? [If used of course...ie Stock primary]

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        • #5
          Originally posted by Racepres View Post

          Sounds like a bad thought process!!!... should always let the engine "talk to ya" ... a dry sump system.. operating properly, will function just fine on a quart or less!!! BTDT

          Jim... I also have heard of sumping into the primary... My Brain just cant wrap around that!!! Can we assume enough oil got into the cam chest that it went to the Primary via the evacuation hose???? [If used of course...ie Stock primary]
          Or seeps through the sprocket shaft seal, or between shaft and spacer, over a long period of time.

          Jim
          High Point, NC

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          • #6
            Originally posted by JB in NC View Post

            Or seeps through the sprocket shaft seal, or between shaft and spacer, over a long period of time.

            Jim
            Really!!! Never thought of that "path"... but, it actually makes more sense
            Thanks

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            • #7
              Originally posted by Racepres View Post

              Sounds like a bad thought process!!!... should always let the engine "talk to ya" ... a dry sump system.. operating properly, will function just fine on a quart or less!!! BTDT

              Jim... I also have heard of sumping into the primary... My Brain just cant wrap around that!!! Can we assume enough oil got into the cam chest that it went to the Primary via the evacuation hose???? [If used of course...ie Stock primary]
              The new oil pump wasn't my idea, in fact I didn't want to do that, but grandpa said to fix what the customer said was wrong then fix it right. It had been to two other shops already so I knew they were missing something.

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              • #8
                Some really good insight- thanks Jim

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                • #9
                  I'm always impressed with Jim's knowledge - AND he used "thence" in a sentence! Hat's off.

                  Shupe

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