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1972 Combat. Setting the new 932 Amal Premier: a nightmare!

Discussion in 'Norton Commando Motorcycles (Classic)' started by pierodn, Apr 12, 2018.

  1. gtiller

    gtiller VIP MEMBER

    Nov 5, 2012
    @cliffa yes, from a visual check, it looks like the hole in the end is the only one that’s different between the #17 and #19 jets, so I think we are safe to assume that’s the only part that is metered.

    So you are going to drill the pilot jet through the other side via the adjuster screw hole to save you from taking the carbs off the bike? Nice idea - although swarf will be minimal it would be neat to be able to drive it out with an airline and/or vacuum as you go.
  2. cliffa


    May 26, 2013
    Yep, that's the plan gtiller. Good idea about the swarf, I actually have a tin of "Air duster" which should do the trick I think. If you have a pilot jet in front of you would it be possible to estimate how deep I need to go from the tip to the side feed holes (to ensure I've drilled out the hole completely)?


  3. gtiller

    gtiller VIP MEMBER

    Nov 5, 2012
    Yes, you’re looking at about a quarter of an inch.
  4. cliffa


    May 26, 2013
    Thanks very much gtiller. If it works I'll post some pics. etc.
    gtiller likes this.
  5. htown16


    Apr 29, 2009
    To determine if you need to enlarge the idle jet from 17 to 19 do this test. With the bike running turn the mixture screw in making the mixture richer. If screwing it in a half turn or 3/4 turn makes the bike run better then you need to go to the larger idle jet size. If it is no change or worse, enlarging the idle jet will have no effect or worse. Someone has said the increase from 17 to 19 is roughly equivalent to a 3/4 turn in on the mixture screw. These things can be a bit finicky. I put new Premeirs on my Trident. They came with 17 idle jets. Bike wouldn't idle at all at 1 1/2 turns out on the air screw. I gradually turned the air screws in I could hear the idle pickup. They ran best at 1 full turn out. So I thought okay a set of 19's should be really good so I got a set and installed them. Bike wouldn't idle for crap no matter where I set the mixture screws. Put the 17's back in, mixture screws 1 turn out, runs sweet again. Both my 72 and 74 Commando's with Premiers idle well with 17's and the standard 1 and half turns out. Point is you will probably have to experiment with your bike to find what works. They all seem to be a bit different.
    Last edited: May 10, 2018
  6. MichaelB

    MichaelB VIP MEMBER

    Jan 14, 2004
    It’s been said earlier, the needles to be matched to the spray tube.
    The straight spray tube needs the 2 ring needle.
    The notched spray tube needs the 4 ring needle.

    These are not the clip rings, but identifying rings just below the tip top, above the first clip ring.

    Cannot tune a carb with mismatched needles / spray tube.
    Last edited: May 11, 2018
  7. MichaelB

    MichaelB VIP MEMBER

    Jan 14, 2004
    If you haven't seen this, here's a good read.


    Notice down at the pilot it says "The bush has a flow rate, equivalent to 20cc/min."
    So why would 17's be fitted an the new??

    Notice the needles.
    "Needle Markings. (600 and 900 Series Concentrics)
    Needles have inscribed rings or letters stamped at the head of the needle above the clip grooves. All needles use a constant diameter down to the head of the tapered section. The taper helps to manage the transition from the Needle jet to the Main Jet and varies according to the type of engine or fuel."


    Markings Where used Part No:
    1 inscribed ring 2 Stoke, 600 Series 622/063
    2 inscribed rings or 'U1' 4 Stroke, 600/900 Series 622/124
    3 inscribed rings or 'X' 2 Stroke, 900 Series 928/063
    4 inscribed rings Norton 850, Triumph 250cc 928/104
    5 inscribed rings Triumph T160 622/278
    Y Alcohol, 600 Series 622/099
    Z Alcohol, 900 Series 928/099

    And the spray tubes
    Interchangeable Parts
    Spray Tubes


    "As a general rule the most noticeable difference between a 2 Stroke and 4 Stroke carburetter is the spray tube. The brass tube is visible as you look through the carburetter bore. 4 Stroke spray tubes are cut off straight, whereas 2 Stroke spray tubes are cut off at an angle, sloping towards the mounting flange. Some later '850cc Norton Commandos' use a spray tube with a square cutaway step. Triumph Triples use an angled spray tube cutaway from the mid point of the spray tube, rather than right across, as in the 2 stroke version. 2 Stroke and 4 Stroke bodies are not interchangeable and will not run correctly if used on the wrong type of engine."

    Notice Norton is only called out on the Notched tube and 4 ring needle. I believe these were only used originally in the Black Box 850's, 2A's and 3's.
    They will work in other applications but need to be matched.

    The straight or 4 stroke tube was in all others including the Combat, orignally.
    What it doesn't say is the 2 ring needle goes with the straight or 4 Stroke spray tube.

    The needle may or may not be correct. But it does need to be verified.

  8. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Nov 20, 2004
    The Premier pilot jet and old jet bush are sized in thousanths of an inch (17 = 0.017") not flow rate.

    Page 2

    The stepped spray tubes and 4 ID ring needles were in fact fitted to all 850s.
    Last edited: May 11, 2018
  9. pierodn


    Nov 10, 2012
    The new 932 premier was sent back to Amal because was faulty for me.
    Were impossible to set.
    To day is arrived the replay from Andover:
    “Burlen have tested the returned carburettors. They agree one of them is faulty.”.
    They dont say what was faulty.
    It should be good to know what.
  10. Mr. Rick

    Mr. Rick VIP MEMBER

    Feb 6, 2009
    That was not very helpful of them. We all want to know what the problem was.
    Please let us know how the new one works out?
  11. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    It is very worth while checking these carbs before installation. Two weeks ago I bought a new matched pair of 850 Commando Premiers. Came in the correctly labelled sealed box etc. Sold through British Spares in NZ.

    On checking I found one had a 260 main jet. Correct for this model 850. But the other carb had a 200 main jet fitted. I considered the possibility of the 2"0"0 being a miss stamped 2"6"0 so had the size checked with a guage by a friend. It definitely matched the other 200s we had. So wrong straight out of the box.

    The rest of the carbs were OK. The 106 needle jets were on the loose side of guage but not as big as 107. The needles,slides and spray tubes were correct. The pilot was a 17 (two band markings) so I will probably change it to a 19 (three band markings) before installation.

    The good old "quality control" of British industry continues on ;-)
  12. pierodn


    Nov 10, 2012
    The new Premier was sent back to Andover.
    After a ten days they Amal replayed me that one of the carbs was fault.
    But they didnt say me what.
    Andover will send the new carbs.

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