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Looking for an air leak

Discussion in 'Norton Commando Motorcycles (Classic)' started by Pete Komarek, Mar 26, 2019.

  1. Pete Komarek

    Pete Komarek

    Sep 8, 2018
    Rebuilt 850 MKIII with new valves, etc. Good bore and pistons. New Wassell Evo carbs with 319 pilots and 260 mains. First ride out Sunday. Bike started well on choke and tickle, did not like going off choke. Horrible bog on the bottom. Same as with old carbs.
    Will run on choke at low throttle only. When it gets on the main jet runs great.
    I suspect an air leak. I have checked-
    -Intake manifold and carb sealed with anaerobic sealant. carb tops and float bowls are tight.
    -Just set the valves will check them again.
    -I'm going to pinch off the balance tube on the intakes to see if it shows more on one side.
    -Plugs are light tan on one side but I used the choke to get low end and take off.
    -I'll spray the intake joints with ether to check for obvious leaks
    -Any other places to check? Has anyone seen air leaking from the intake mounting threads on the head?
  2. dynodave


    May 28, 2003
    Amal 850 was 3-1/2 with 260 main...

    Isn't Wassel 850 supplied 3(rich) cut away slide with 220 ? 260 would be super rich at low end/off idle.
  3. Pete Komarek

    Pete Komarek

    Sep 8, 2018
    I bought these set up for a Norton. I'll have to check the slides. I have a k&N filter and peashooters on it. Pulls well once on the main jet.
  4. Douglass Harroun

    Douglass Harroun

    Sep 12, 2008
    I had this with a new build on a Triumph. Needed richer slide
  5. htown16


    Apr 29, 2009
    Might try raising the needle a notch. Mines in the bottom notch (richest) on my 750 and its just on the edge of lean. Doesn't cost anything.
    Pete Komarek likes this.
  6. Pete Komarek

    Pete Komarek

    Sep 8, 2018
    No effect spraying on the intake joints. No effect blocking off the balance tube. I'm going to try advancing the timing. Currently Lucas Rita, may be old and not advancing properly

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