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Norton Commando Compression

Discussion in 'Norton Commando Motorcycles (Classic)' started by Norton_Commando_Neil, Sep 9, 2003.

  1. Norton_Commando_Neil

    Norton_Commando_Neil

    Joined:
    Sep 9, 2003
    The problem I am having with Norton Commando 850 MK2A interstate 1975 is the plugs seem to be black all the time, I have tried all settings form the manual but am unable to get the rusty brown colour it should be. The bike has peashooter exhausts, no balance pipe between exhausts and the black box air filter behind the Amal MK1 carbs, I also use Castrol Valvemaster additive in the petrol. The throttle needles are set in the top groove so it is in its lowest position. The bike also pops through the exhaust if the mixture is weakened too much to try to get the right colour. I intend to check the compressions incase there is wear on the valve guides and the bike is sucking air, the timing has recently been done and is spot on and the carbs have been stripped with new gaskets and have all the correct jets fitted. Can you tell me if I am following the right lines here?

    Thanks,

    Neil
     
  2. Jerry Doe

    Jerry Doe Admin

    Joined:
    May 21, 2003
    Hi Neil,
    What kind of ignition do you use? Did you check it?
    Jerry
     
  3. Anonymous

    Anonymous Guest

    It is a Boyer electronic ignition

    Neil
     
  4. Roger

    Roger

    Joined:
    Sep 14, 2003
    check throttle needles and proper position of clip or damage to either seat for needles.Sounds like you can't adjust the mixture. which means pilot screw or throttle needles stuck open. How does your machine run? good power or does it bog out? or break down at higher rpm?
     
  5. Norton_Commando_Neil

    Norton_Commando_Neil

    Joined:
    Sep 9, 2003
    Hi
    The bike runs well with lots of power, the only trouble is the rich mixture on one side. Should I try another carb on?
    Neil
     
  6. Roger

    Roger

    Joined:
    Sep 14, 2003
    RE-compression

    Hi Neil have you found a solution to your problem?Could you post your results when problem solved? It helps us all when following the trials and tribulations of other NORTON owners thanks.
     
  7. jimboyle

    jimboyle

    Joined:
    Aug 11, 2003
    compression

    Neil,
    your exhausts look a bit blue for a bike with a rich mixture. Could it be that the valve guides are worn and you are burning some oil which is blackening the plugs. A compression test will not find worn guides, the only way is to take the head off.
    My MK11 had done 27000 miles and the guides were really well worn

    Jim
     
  8. Norton_Commando_Neil

    Norton_Commando_Neil

    Joined:
    Sep 9, 2003
    I agree the exhausts do look blue, The valve guides are a thing that I have been considering for some time. I intend to carry this out hopefully the beginning of 2004 but will need help and advice as I am not familiar with such tasks. Regarding the black plugs, the bike is run for approx 2000 miles per year in which I never have to refill the engine oil level. (I don't think its burning oil) Can someone give me an approx cost to have this valve work carried out if need be?

    Thanks,

    Neil
     
  9. jimboyle

    jimboyle

    Joined:
    Aug 11, 2003
    compression

    Neil,

    i don't know how much to have this done in a shop, but the head overhaul kit from RGM is £58, this give you 4 valves, guides, the springs, seals and heat washers. It is not difficult to to, you have to heat the head in your oven so you can knock the guides out and in and if you remove the rocker spindles to make it easier it can be fiddly getting them out and in with the hot head. i made a brass drift to knock the guides out and in but you can buy special tools, all shown in the workshop manual, if you don't have one i would be happy to e mail you the pages. A bike mechanic would be much quicker than me but you are still looking at a few hours work so probably £100 labour

    Jim
     

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