Results 1 to 9 of 9

Thread: Priming an oil pump before use

  1. #1
    48Chief Guest

    Default Priming an oil pump before use

    I am completing a frame off restoration on a 39 Chief and have read these oil pumps must be primed before use when drained.

    What is the procedure for priming an oil pump? Is it as simple as filling the pump through the recirculating tube prior to filling the tank with oil? Or is there any other process involved?


  2. #2
    T. Cotten Guest


    There are two parts of the 'cast iron" Indian pump: the feed plunger, and the sump return gears on the bottom.

    The sump is ironically the most critical. Turkeybaster a few ounces into the motorcases through the timing port before you start. Most serviceable units will quickly pick this up and return it to the tank in a matter of 20 or 30 seconds at most. Avoid in-tank filters, until you have passed this step!
    Proper testing must be done on a bench at 500 rpm, ****ing air after drawing oil, then closing the return completely to hopefully read 30 psi on a gauge. (Repair is often only a matter of grinding the cover flat, and replacing the gears with ones of quality.

    The feed side should pump a minimum of 60 cc per minute, often producing only about 1.8 to 2.5 psi. Even worn units manage that easily. Priming it should only be a matter of patience, as sitting overnight with a tankfull of oil will normally bleed past to fill it it anyway.
    Make certain on your early version of the pump that the cap over the plunger has a cylindrical "tit" protruding beneath it. That's a critical "bubblebuster".

    John Bivens, Ron Link, Vern Goodwin, and even Starklite all offer testing services.

  3. #3
    48Chief Guest


    Very good info, thank you.

    I never broke into the cases as the motor had been rebuilt 3000 miles or so ago, but totally drained the cases and left the oil plugs out for several months slowly dripping as I restored the bike. I can only assume the pump drained as well. I guess before I assume any drastic precautions I'll fill it and let it set over night. If she dosen't pump I'll take it to the further steps you laid out.


  4. #4
    T. Cotten Guest


    Please let us know what you observe!

    It is curious that the filters on this site bleeped out s,u,c,k,...but let "tit" through.

    You would think they would go together!

  5. #5
    AdminGuy Guest


    I don't have the "bubble buster" shaft. Would like to up-grade. Can you give me a few dimentions for it? w, h,

    How can I tell if my breather valve is functioning correctly?

    Is a breather line off my cast pump nessesary or can I plug the hole?

    I didn't drill the wrist pin bushing oil spash hole, center. Please tell me it's not critical as I have plenty of clearance side to side. Y-Manifold went on real sweet with loose base nuts. Nice alignment, good contact and fit.

    My lump'o'iron is quickly takeing shape now.

  6. #6
    T. Cotten Guest


    Sorry, but I do not know if I have a castiron pump handy to measure the cap.

    The best way to be certain a Chief breather works is to get a Motovalve from, and put the original on the shelf.
    For a Scout, I guess you had better go by the book. Certainly it must vent somewhere.

    I guess we shall find out if the splash hole is critical with your next top end. Let us know!

    And you cannot trust to luck on a manifold. Please pressuretest it as per
    (Note that Sport Scouts are subject to damage to the nipples into the cylinders themselves, as often over-length headbolts have crushed them.)

  7. #7
    AdminGuy Guest


    Thanks Tom, Rigged up a piece of 1/4" plex with old bicycle inner tube valve, and rubber for compression seal. Both brass rings leak. Uggghhh..... Pls send PEEK seals asap. We'll do a flip-flop in trans exchange.

    One barrel has helicoil insert over intake nipple. So figure someone goofed in past. Hopefully it will not leak.

    Gutted some chief stuff for my breather disk. Almost forgot it. It looks to simply function as a baffle. Solid -not drilled. What makes Duffs better? Ahhh... it's a modern PCV valve. I see now. Sadly won't fit on scout oil pump.
    I see why 741 cases better for stroker. Timing plug hole used for breather.

    But what can I do for my 640?

  8. #8
    T. Cotten Guest



    Fitting PEEK ferrules is a custom-cut operation, as often the spigots are worn and must be re-cut. And often there is great variance in the nuts, particularly from one Left-Coast source that might even sell a pair that don't even match each other!

    I prefer to have the hardware in hand so I can assure a perfect assembly.

    And please find a big rubber stopper, or carve a cork or something to pressuretest the nipple in the cylinder itself, as well as the bolthole over it.

    (Note that using a Schrader or tire valve does not allow a constant supply of regulated air, as often needed for testing for the tiniest of leaks.)

    The Motovalve isn't really a modern PCV unit, but rather a piloted disc that seats more accurately, and is a less restrictive casting (although it looks identical on the outside!) An e-mail to Duff at the address in my first post might come up with a better Scout solution.

  9. #9
    AdminGuy Guest


    Taking this over to the scout section.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts