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norton 1957 99 timming

Discussion in 'Other Norton Motorcycles' started by mark375850, May 2, 2019.

  1. mark375850


    Nov 2, 2011
    can anyone tell me correct timming for a 1957 model 99 i have two different manuals telling me a different setting
  2. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    I have two Norton publications, Maintenance and Instruction Manual Publication P106/P, and Twin Cylinder Manual (no publication Number), neither of which has a publication date.

    Both of these manuals state 32 degrees full advance for Model 99.

  3. marinatlas


    Nov 4, 2007
    according to PL. Garrat : 32°.
  4. Bernhard


    Apr 20, 2011
    Just to throw a spanner in the works, 32 degrees is right if you have original low compression pistons, however, if you have, say, 10.5 C.R. then its less.
  5. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013

    According to my manuals (cited above), the Model 99 CR was 8.2. Thus with up to 9.0 CR, I would not expect any pinging with 93 octane petrol.

    FWIW, I have just made the following changes in CR and timing in my Atlas:
    CR = 10.5 and timing 30 deg full advance changed to CR = 9.0 and timing 32 full advance. With 93 octane fuel, I am not having any pinging, whereas with CR = 10.5 and timing = 32, I had to be careful with the throttle to avoid slight pinging.

  6. Paul W.

    Paul W.

    May 12, 2018
    Are you using ethanol free gasoline?
  7. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
  8. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    Hi Mark

    In NZ I'm guessing you are using pump 95 or 98 for your 600.

    NZ 98 usually has up to 10 % ethanol in it. Other octanes can as will and its a bit of a challenge some times to find out what does and does not have ethanol in it.

    The good news in my experience is apart from ethanol eating fibreglass tanks - no a problem for you - it doesn't make much of a difference. I raced a Norton Dommie in NZ classic racing for many years. I had 10.25 :1 CR.

    I tested No 1 race fuel back to back with NZ 98 pump gas Mobil and could see no difference on the dyno or on the track. I know ethanol has less energy per unit volume than normal petrol but maybe I was just running a bit rich.

    I did lots and lots of dyno testing. Changing ignition timing from 28 up to 31 degrees was one of the variables. In the end I used 28.5 on the 500. Your head shape will be very similar to the 500 and unless you have some nasty domed piston in there you wont really be much different to the Dommie.

    So if your running NZ 95 or 98 I would use around 28.5 to 31 depending on CR. Higher CR 28.5. Low CR 31.


    Unless you have converted to EI - CHECK THE TIMING ON BOTH CYLINDERS

    Old magnetos and points systems can easily have 10 deg different between cylinders. Fixing this is way more important than getting street bike ignition down to the last degree.

    I'm confident in this advice. Once I sorted the bike we had over 150 races without a DNF. And won about 5 NZCMRR club championships including 2 seconds in the NZ Classic TT at Puke and Hampton Downs against Manx Nortons etc.

    Get the timing the same on both sides - that is critical. The last one or two degrees of advance used is not so critical especially on a street bike and would probably require dyno testing to tune for an individual machine anyway.
    texasSlick likes this.
  9. texasSlick

    texasSlick VIP MEMBER

    Jan 2, 2013
    If you have a magneto, check the point gap on both ramps. If these are not equal within 0.001", it is a virtual certainty the timing will not be the same on both cylinders. You can expect 2 degrees of timing mismatch for every 0.001" difference in point gap

    Report back your data .....


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