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Another Norton resurrected

Discussion in 'Norton Commando Motorcycles (Classic)' started by WEM, Jul 1, 2018.

  1. WEM

    WEM

    Joined:
    Dec 8, 2017
    I haven't posted for awhile but I wanted to advise that my 1974 Roadster is back in action after sitting idle for 27 years! She's running pretty rough, but I'm amazed she started at all. Thanks to everyone who offered advice.
     
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  2. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Well done mate,any photos?
     
  3. WEM

    WEM

    Joined:
    Dec 8, 2017
    Unfortunately, it looks like my initial excitement may have been a bit premature. The bike started easily, usually first or second kick, but she was running very rough with less power than I seem to remember. (It's been 27 years so memory might be an issue). Some diagnostic work indicated that the left cylinder is not firing as well as the right. Left exhaust pipe is much cooler than the right. Right plug is a nice light grey color, left plug is coated in dry black soot material which I believe means that cyclinder is running too rich. Carbs have been checked and adjusted, new plugs and plug wires have been installed. Compression is good on both cylinders. Spark across the right plug is strong but spark across left plug is present but barely. Coils have been checked and are at specified resistance. Wires to left and right condensers were switched with no effect: left cyclinder still had weak spark. I suspect an electrical problem (it has been suggested that it might be a valve issue but I'm really hoping not). One of the connections to the left condenser is showing some corrosion, the others are fine. I'm not sure if that corrosion is enough to cause a serious reduction in spark at the plug. Connector will be replaced. Does anyone have any other ideas?
     
  4. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Sure do. Clean up your ground points.
     
  5. Mr. Rick

    Mr. Rick VIP MEMBER

    Joined:
    Feb 6, 2009
    Does a plug (or plug wire) swap move the problem over to the other side?
     
  6. WEM

    WEM

    Joined:
    Dec 8, 2017
    The plugs and plug wires were swapped. Not at the same time, with no change in the situation.
     
  7. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    Unplug the condensers and check the spark - it will run OK for a few minutes without condensers. If no joy, disconnect the coil wire and check resistance from it to the engine casing on the lowest setting on your meter with the points closed - you want 0.
     
  8. grandpaul

    grandpaul VIP MEMBER

    Joined:
    Jan 15, 2008
    Did you check your valve lash settings?
     
  9. WEM

    WEM

    Joined:
    Dec 8, 2017
    Thanks for the suggestions. I'm in the process of going through the wiring to see if there are any loose or corroded connections. I really hope it is something as simple as a wiring issue and not something more mechanical like a valve issue.
    What is the valve lash setting supposed to be set at?
     
  10. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    Hi WEM, given that you are reporting a weak spark on one side leads to an electrical solution, not valves. But you say you have a stock 74 850 so use a .06 inlets and .08 exhausts if you feel you have some time after solving this electrical issue and want to check the valve clearances. Just a thought, your wiring is some 45 years old, ground wires went to frame mounts and not properly back to the positive battery terminal, live current goes to the headlight area and back through kill button, just lots of places for failures and partial connections. You did not state if points or EI ignition? Pull the points cover off and check the wiring connections in there, clearly some wire somewhere is not delivering strong spark to that weak side. Could be a partially fracture wire coming back up out of the points and along the front down tube, could be anywhere at this point. If points it could be as simple as checking the point gap on the weak spark side, if points anyway it is time to upgrade to EI like a digital boyer, pazon, trispark etc and never worry about sticking auto advance or moving points gaps again.
     
  11. WEM

    WEM

    Joined:
    Dec 8, 2017
    The bike still has points. The plan was to make sure she was running reasonably well before investing in EI and a bunch of other things on my wish list. May have to consider going to EI sooner than I thought. In the meantime, I'll follow through on your suggestions which are really appreciated. This forum is a godsend for guys like me who don't have tons of experience dealing with Nortons. Thanks again.
     
  12. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    The points have a wire return to battery positive through the head steady 'ground' (red) and the condenser pack base plate should also have a return wire.

    Actually the junction area beneath the fuel tank (is where the switch cluster wires connect to the loom).
     
  13. WEM

    WEM

    Joined:
    Dec 8, 2017
    Managed to get a couple of hours at the bike this weekend. Noticed that the points were sparking pretty good which I think means the condensors might be suspect? They look pretty rough so they probably need replacing anyway. The coils were tested earlier and reading was good but one seems to be working better than the other. When they are switched there was a slight change for the better in spark at left cylinder. Coil also seemed like it was slightly deformed, maybe had been over tightened. Also looked at the carbs. Bike has to idle really high to keep running. I think that means that the low idle setting in one or both of the carbs, which I think is controlled by the pilot screw, is not working properly? Also found some debris in the carbs when I had them off. Cleaned it up but no difference. I'm now wondering if the problem might be a combination of electrical and carburation issues? Rather than try to rebuild 44 year old carbs, would it make more sense to just replace them with new?
     
  14. kommando

    kommando

    Joined:
    May 7, 2005
    Your pilot jets cleaned out with a #78 drill mounted in a W40 red tube with epoxy will restore the tickover, also clean out the pilot air, fuel circuits and the 2 holes coming up into the main venturi from the pilot mixing chamber.

    http://www.jba.bc.ca/Bushmans Carb Tuning.html

    [​IMG]
     
  15. DogT

    DogT VIP MEMBER

    Joined:
    Jan 20, 2009
    When you squirt cleaner into any of the 3 ports with the pilot screw out, you should get cleaner coming out of all the other ports. Otherwise something is dirty or blocked. JBA site is good info for the carb. If the slide is worn too much, you'll never get a good idle. I only had about 12K on mine when it was too loose. Either resleeve or buy new ones. New ones are probably a better deal because they will have all new parts including the anodized slides and stay up floats and easier to adjust float. The points will spark pretty good even with good caps. 45 year old springs on the advance unit are suspect too, as well as being worn to the point of not holding consistent gap. It's possible to re-bush the advance unit, but a Pazon SureFire will work wonders for the sparking and timing and probably be easier. But maybe get it working fairly good first.
     
  16. grandpaul

    grandpaul VIP MEMBER

    Joined:
    Jan 15, 2008
    Before you tear too many things apart, it's a simple check to see that you don't have a valve rocker way too loose or way too tight.

    Also, only change/adjust/fix one thing at a time, till the problem is solved.

    I use a 1-gallon can of Berryman's Chem-Dip to properly clean the carbs. Crack the lid open, then set the can in the sun to warm it up. Soak all metallic parts for 30 minutes or a little longer, then flush excessively well with water, then blast the carbs dry with compressed air.

    [​IMG]
     
  17. grandpaul

    grandpaul VIP MEMBER

    Joined:
    Jan 15, 2008
    You can use a piece of "plumber's tape" (fine grit emery cloth) to dress the points. Spray with electrical parts cleaner or WD40 after cleaning.
     
  18. WEM

    WEM

    Joined:
    Dec 8, 2017
    Thanks to everybody for their suggestions. I'm trying to work through them as methodically as I can. Looking at the simpler things first. The carbs are Amal 932's. I just noticed that even with the throttle screws backed all the way out, both slides still stay open about 3/16". Is this normal? I thought that the slides should close completely when the throttle screws were backed out. Both carbs look to be open exactly the same amount. I'm not sure if this is significant or not. Would it be an issue with the throttle cable?
     
  19. batrider

    batrider

    Joined:
    Aug 9, 2008
    No WD40 on the points please.
     
    Nater_Potater likes this.
  20. oldbeezer

    oldbeezer VIP MEMBER

    Joined:
    Nov 2, 2017
    I would definitely check the throttle cables. Sounds to me like they need adjusting. Does turning the handlebars side to side affect the idle speed?
     
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