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1965 FLH Primary Chain Case Venting

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  • 1965 FLH Primary Chain Case Venting

    I'm bringing a 65 FLH back to "original condition", or as close as my pocketbook will allow me to. As anyone who has undertaken a 65 knows, there are many one year only or mid production changes that exist on this year. The issue I'm currently trying to solve is, or if, how the primary was vented. According to the parts manual, there was no tee in the vent line between the motor and the oil tank which is the normal method of venting the primary chain case on late 66 and up models. The parts manual does list a "vent kit" which includes a tee, clamps, & vent line, with a -66A part number that fits 1965 and later models. My understanding of this would be that the MoCo added the tee method of tying into the motor to tank vent line, via this kit, sometime in 1966. Can anyone provide any information describing how the 1965 & early 1966 FL primary's were vented. Thanks very much for any help you can provide!

    Last edited by 67sidecar; 11-06-2020, 07:13 AM.

  • #2
    IIRC there is a line form the inner primary back to the oil pump. A lot of folks did away with that as who wants dirty primary oil going back into the oil tank. Some I have seen just run an short piece of line out and let it go on to the rear chain with soem kind of filter so dirt doesn't get back to the primary. Sorry that I can't be more helpful but my latest pan is 64 so not and issue for me.

    Tom (Rollo) Hardy
    AMCA #12766


    • #3
      I read somewhere, 67sidecar,...

      That Palmer's third edition might cover '65s!

      My ""stocker"" KCPD refugee was "vented" by a starter oil deflector without an O-ring, and ironically without a drain hole in the starter housing.
      (Lost a DELCO to water sucked in.)

      "Up-dated", and it ran great for decades "unvented", except for leaks.

      Gotta love '65s.

      PS: I was told it was a KCPD machine when I bought it. That's my narrative, and I'm sticking to it.
      Last edited by T. Cotten; 11-06-2020, 04:58 PM.
      AMCA #776
      Dumpster Diver's Motto: Seek,... and Ye Shall Find!


      • #4
        65-E66 models did not have vent in the inner primary

        Ran my 65 FLH this way from 1970 until 2000 when I finally decided to save up for a rebuild and stopped riding the bike.

        Last year I finally started the rebuild process. During the ensuing years I had collected parts and stuff to put it back together close to stock but with a few additions/updates, one being the vented chaincase.

        It is my understanding that in 1966 HD changed to the vented primary and that this what it looked like. The Service Bulletin for the retrofit is dated 3-66 so that would coinside with what you are saying as well.

        Have to add that I never had any leaking because the primary wasn't vented. Got the ususal drip as the gasket wore out between the inner and outer primary. I wasn't much for changing gaskets eveytime I took off the outer primary.
        Attached Files
        Last edited by panz4ever; 11-09-2020, 03:49 PM.


        • #5
          What's a spare inner like that worth, Folks?

          Askin' for a friend,...

          AMCA #776
          Dumpster Diver's Motto: Seek,... and Ye Shall Find!


          • #6
            Here's a later instruction sheet and Service Bulletin 538A.


            • #7
              Interesting to see the later instruction sheet. What i posted is what came with the kit, instruction sheet and parts.


              • #8
                Thank you guys for providing such detailed information, it's cleared up the mystery! I'm going to assemble it as a "vented primary" bike with all of the modifications listed in the instruction sheets, and deal with any purists who point out it 65's didn't come "vented" as they come. At least now I know the facts and can defend my choice. Thanks again, what a wealth of knowledge! Best Regards, Bill