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Aluminum float needle/viton tip, made to be light weight to solve any seating problems.

Discussion in 'Norton Commando Motorcycles (Classic)' started by jimbo, Oct 12, 2019.

  1. jimbo

    jimbo VIP MEMBER

    Joined:
    Sep 25, 2004
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels

    "Needle Valve


    If your float chamber is fitted with a brass needle valve, you may find the valve sealing under its own weight, before the float has risen far enough to press it shut. Symptoms of this problem can be that the carburetter takes a long time to tickle, hesitates on pickup and does not idle reliably. A Viton tipped aluminium needle valve is now available that overcomes this problem. It is now fitted as standard equipment to all new Mark 1 Concentric carburetters."
     
  3. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    I heard the thinking is the lighter weight alu needles are easier for the float to lift off the seat when needing more fuel. When needing to close down flow, the float buoyancy provides enough force to hold the seal closed.
     
  4. Steves

    Steves

    Joined:
    Oct 16, 2016
    Whatever, they work great!
     
  5. joe czech

    joe czech

    Joined:
    Feb 21, 2019
    FWIW, they're standard in the latest amal rebuild kits - ;)
     
  6. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    There’s a lot of free play between the float fork and the needle.

    If the head of fuel can lift the needle when the tank is full, but not when it’s only 1/4 full, you’ll have a variation in float bowl fuel level.

    The ally needle is supposed to be light enough to be lifted open by the petrol under all conditions.
     
  7. xbacksideslider

    xbacksideslider VIP MEMBER

    Joined:
    Aug 19, 2010
    Gimme brass please. It doesn’t get fouled by that white grunge that grows on aluminum when exposed to the moisture that the corn ethanol absorbs
     
  8. tri-man

    tri-man

    Joined:
    Nov 10, 2014
    I remember well how excited I was when I could get brass and Viton needles, and how they would solve problems I didn't know I had. Long time ago.
    Now I'm going the other way, I save every single nylon float needle I can find and retrofit them. I used to have all kinds of issues with my 72 Trident, slow tickling, long warm-up, inconsistent idling and persistent float bowl leaks. After I changed back to nylon, all these issues simply went away.
    To recommission nylon needles I use chrome polish on a piece of cloth, and I clean the float seats too with polish on a Q-tip.
    Aluminium needles may be great for what I know, but as long as I can find nylon ones I'll fit those.
    I might add that I use chrome polish to clean needles and seats on modern carbs as well, and it works even on Viton.
     
  9. illf8ed

    illf8ed VIP MEMBER

    Joined:
    Dec 30, 2003
    I wonder if engine vibration which is considerable is considered. More mass (brass) will tend to dampen the effect wouldn’t it? However any material will have a frequency resonance that will break the seal between needle and jet. I guess if it works don’t mess with it either brass or aluminum.
     

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