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Uneven run up to 3000 rpm

Discussion in 'Norton Commando Motorcycles (Classic)' started by Woody850, May 13, 2018.

  1. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    I have addressed this in a similar thread but I now encounter other problems in that when running the bike for the first few miles all is well but once warm she begins to run unregularily, popping and cutting out for a second.
    I am still waiting for my #19 pilots for the premiers and have the needles on the middle notch but still don't think the problem should be getting worse which it is. I've checked for air leaks at the headers but find none. I don't have a balance pipe either. As said this is in the lower rev range up to 3000 which points to the carbs I believe. I fear taking the bike out at the moment.
     
  2. kommando

    kommando

    Joined:
    May 7, 2005
    Carb issues related to throttle position, electrical issues are rev related. So mark your throttle at 1/4, 1/2 , 3/4 and full and see what throttle opening gives you the issue, if it's not related to throttle but still at 3000 then start looking at electrics.
     
    ewgoforth likes this.
  3. JimC

    JimC

    Joined:
    Oct 12, 2007
    Do you have an electronic ignition?
     
  4. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    Yes I have a Boyer and the contacts seem ok at the contacts and well insulated
     
  5. JimC

    JimC

    Joined:
    Oct 12, 2007
    About a 95% probability one or both wires from the pickup coils have fractured. A visual will not detect this. Use an ohmmeter, twist and shake the wires. Boyers are well known for this problem.
     
  6. Deets55

    Deets55 VIP MEMBER

    Joined:
    Oct 3, 2013
    Had a similar problem. After checking all connections and the Boyer wires in the timing case the culprit turned out to be a bad coil. Bike ran fine till the coil warmed up and then it stared missing.
    Just something to think about.
    Pete
     
  7. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    I had your symptoms and the cause was exactly as Jim states.

    Also, Boyer miss behaves with a low battery. It’s a low probability, but it could be your battery and / or charging system.
     
  8. cliffa

    cliffa

    Joined:
    May 26, 2013
    If you Boyer doesn't have the small piece of rubber sleeve under the cable tie securing the pickup wires (see picture below) it's highly likely that the inner copper strands have sheared and are making sporadic contact. Even if you find they are not broken it's worth changing the connection method. There are many ways to do it, my own is here. As you can see I caught mine just in time.

    I spoke to Boyer some weeks ago about my Powerbox and mentioned this issue, they reckon this piece of sleeve fixes the issue. I would be good to know if they are right, but personally i'm doubtful.




    Cheers,

    cliffa.
     
  9. JimC

    JimC

    Joined:
    Oct 12, 2007
    Also, 85% of carburetor problems are electrical.
     
    Last edited: May 13, 2018
  10. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    Hi Fast Eddie, I tried overcoming the weak battery problem by fitting an 18 AH lump.
    Could the charging system still affect the running if the juice is there.
     
  11. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Not short term no. But if the charging system is not functioning correctly then even an 18ah battery will drain. Then you’ll get the symptoms.

    If your sysmptoms exist even when you KNOW you have a fully charged battery, look elsewhere.
     
  12. eskasteve

    eskasteve VIP MEMBER

    Joined:
    Sep 24, 2012
    Bad coil here, also. Same symptoms.
     
  13. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    I have an old coil from a T140V of mine that would be the same to use as a spare wouldn't it?
     
  14. JimC

    JimC

    Joined:
    Oct 12, 2007
    Did you check the wires from the Boyer pickup coils with an ohmmeter? If not, you are probably going down the wrong rabbit hole with the coil. The probability of the wires fracturing is 100 times that of the coil failing.
     
  15. Steves

    Steves

    Joined:
    Oct 16, 2016
    Plugs? I was in the workshop today, rummaged through a pile of spark plugs, found some NGK Iridiums and thought I'll put those in. Got half a mile, popping and banging, turned round put the old plugs back, no problems.
     
  16. auldblue

    auldblue VIP MEMBER

    Joined:
    Nov 20, 2012
    When the bike starts misbehaving, is it on only one cylinder or both? Obviously you have a good battery charge and have changed the plugs, checked all connections,bad earth , used the Boyer fault finding options , tested the coils (hair dryer for warm test)and checked them for cracks, examined the inlet manifolds for cracks, replaced the needle valves ,cleaned pilots,checked fuel flow and dirt in fuel. It's a process of elimination as I've run boyers down to below 12v and they still start and run, boot it on wot an see what happens. These are faults that I've had on my own bikes over a period, may be of some help!
    You say you don't have a balance pipe on exhaust or inlet?
     
    Last edited: May 14, 2018
  17. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I brought my Commando home dead loss when the zener died, about 300 miles total. That was when I discovered how little actual storage is in one of those highly rated but tiny Li batteries. Luckily it flamed out at the top of a hill that must run for 10 miles down into the scorching hot desert town of Osooyos BC.
    Its also a dessert town and, much to the amusement of my riding friends I coasted the Norton right into the Dairy Queen parking lot, had a banana split, then bought a new 14 ah lead acid battery.
    That ran the Boyer perfectly for the remaining 250 miles to home.
    Long winded answer about using your 18ah dead loss, but I wanted to recall the banana split on hot day:)

    Glen
     
    Last edited: May 14, 2018
    Nater_Potater and cliffa like this.
  18. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    Sorry for the late reply auldblue, I have just recieved a new boyer stator plate but need time to set it up. I have noted the sleeve on the new one and mine doesn't have it so I could be lucky.
    Your list of searches I will follow, the carbs are new and work fine except for the #19 pilots which are still in the post. I had meant no balance pipe on the exhaust but the manifold balance pipe is in place.
    On my T140V I junked the air slides, unfortunately for me the choke lever was mounted on the left manifold facing downwards on a through drilled hole, I need say no more. The last restoration I did was a Ducati 900ss which ran well on the old carbs but also kicked around at 3000 rpm. New needles and jets cured the problem completely but it all took time and I ask myself how long this one will take.
    One question, what would be the ideal way to replace the boyer stator with the new one?
     
  19. Woody850

    Woody850

    Joined:
    Sep 30, 2017
    Ok, I got the #19 pilot jets and she runs much smoother in the lower range.
    As mentioned I checked the contacts and the earthing. I can't be 100% sure but my suspect was the ignition switch which was loose and not grounded on the frame.
    Of came some paint and I laid a copper washer to get it tight. After that she didn't kick around.
     
  20. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    The ignition switch doesn't need to be 'grounded'.