Announcement

Collapse
No announcement yet.

7 UL engine problem

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 7 UL engine problem

    MAP_3977_5363 (2).jpgMAP_3975_5361 (2).jpg
    I have a 47 UL. Acquired the bike with the engine rebuilt. Has about 4 thousand miles on it as best as I can discern. Took me a little while to get the bike set up how I wanted and even longer to do any miles on it.
    Everything is set to factory spec. Points properly adjusted, valves timing seems ok. Fitted with Champion D16 plugs
    The bike fires up fine, ticks over ok when warm and accelerates ok up to about 55 /60 mph but then seems to run out of steam.

    I finally did some riding on it last weekend and did 200+ miles in the saddle. Mixed freeway and back roads. Towards the end the bike started to backfire very occasionally. Not very loud but noticeable to the me. Couldn't work out what was causing it before I got home.

    When the engine cooled I pulled the plugs, See the attachments. Front has a nice sooty rim but the electrode is clean as a whistle. Rear cylinder is a much more even light brown colour. I was struck by the difference and wondered whether I have a problem or whether this is not uncommon in 1200 flatheads.

    On checking the bike over I found that the rear exhaust pipe had worked lose where it exits the cylinder. Otherwise it was fine

    Not sure if I have a problem with the motor or not.

    I know flatheads don't like sustained high speeds (neither do I for that matter ) but I do want the engine to be running right.

    My next investigation was going to be a manifold leak down test but I don't have access to compressed air so this will take while to set up - or am I looking for a problem that doesn't exist?

    Would welcome input from those out there who know the big twin flathead engines

    Thanks

    Martin

  • #2
    Martin!

    The first diagnostic is always to bubble-test: http://virtualindian.org/11techleaktest.html.

    Eliminate the variable of a vacuum leak, and the rest falls into place much easier.

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

    Comment


    • #3
      The backfire that developed is likely from that exhaust leak...
      I'd follow Cotton's advice on the bubble test for your other issues...

      Comment


      • #4
        Thanks Guys. I was thinking that was where I needed to look
        Assuming a leak is detected will I need to strip down the whole manifold set up and start from scratch or is there a quick fix to try first
        Assuming I need to strip down has any body experience in using the peek seals I hear about?
        Are they as good as suggested in the advertising?
        Thanks
        Martin

        Comment


        • #5
          Martin!

          Any goober or bandaid will come back to bite you when a digestive fuel eats it.

          And I do have some experience with PEEK seals, as I pioneered their use: http://virtualindian.org/9techpeek.htm, so I must warn you about fitment.
          There is no one-size-fits-all solution, but fitted seals are guaranteed.

          ....Cotten
          PS: The price went up since 2000 as well!: https://www.mscdirect.com/browse/tn/...vid=4287921828
          Everybody is welcome to cut their own!
          Last edited by T. Cotten; 07-13-2015, 05:21 PM.
          AMCA #776
          Dumpster Diver's Motto: Seek,... and Ye Shall Find!

          Comment


          • #6
            Ok thanks Cotton - I will test for leaks and if as expected there are some bubbles present I will strip the manifold down and send it off to have the new seals matched. I am in the UK and I see a company in Amsterdam offering this service.

            Thanks for the input

            Martin

            Comment


            • #7
              Martin!

              Please ask that they maximize the outside diameter within the nut, as original seals were small to allow the brass to "spring".
              PEEK is compliant, which is why it seals easier, but needs the extra dimension to retain its tensile strength, support the assembly, etc.

              Seals of original dimensions need more initial re-torques, with occasional consequences.

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

              Comment

              Working...
              X