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Excessive engine noise

Discussion in 'Norton Commando Motorcycles (Classic)' started by timmyC, Jun 10, 2018.

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  1. auldblue

    auldblue VIP MEMBER

    Joined:
    Nov 20, 2012
    It's the auld joke, "if the noise stops ,... We're walkin"

    Bike sounds nae better or nae worse than most Mando's I've heard runnin!
     
    Nater_Potater likes this.
  2. rvich

    rvich VIP MEMBER

    Joined:
    Jul 25, 2009
    You can run the bike for a short period without valve covers to make sure you are getting oil to all the rockers. The comment about excessive gap caused by wear that is bridged by the feeler gauge is worth paying some attention to. So is the comment about not idling the bike for extended periods. It is also worth noting that a Combat has a tall cam and the movement of the valves is exaggerated. This does nothing to ease the noise, particularly at idle.

    Can you ride without a helmet where you live? A trip down the street at higher RPM without a helmet lets you listen to the bike at different RPMs. Mostly you should be hearing exhaust at that point.
     
  3. Nater_Potater

    Nater_Potater

    Joined:
    Apr 7, 2013
    Or, as I remember it, "Valves are like children; if you can't hear them, they're doing damage!"
     
    Northton likes this.
  4. 3 of them

    3 of them

    Joined:
    Jan 22, 2018
    a happy tappet is a clappy tappet .Sounds pretty typical to me especially for a combat
     
    Northton likes this.
  5. Northton

    Northton

    Joined:
    Oct 18, 2014
    Loud Valves Save Lives
     
    Nater_Potater likes this.
  6. ashman

    ashman

    Joined:
    Jul 10, 2010
    Combat valves run a bigger tappet gap than a normal Commando tappet and will sound a bit louder.

    Ashley
     
  7. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
    TimmyC,
    Do you know anything of the history of the bike? I ask because there are a number of points of concern.. The very low milage ,I would be concerned if it has stood say for 20 or more years without being fired up that oil in the crank might have dehydrated with possible risk of a blocked sludge trap. I have no idea what the recall position in the US was.. In the UK the first batch of combat engined commandos were suffering main bearing failure from around 3,000 miles.
    Dealer stocks here were recalled and fitted with the so called Super Blend main bearings and then the factory changed the production line spec. Now it could be yours was a later combat that already
    had Super Blends , or remedial was carried out prior to sale , or under warranty.

    One of the reasons why the pre Superblend Combats failed was that the new wild cam destroyed the advance and retard. The French Gendarmrie ordered combat engined bikes fitted with the then new fangled Boyer ignition . These ran over 10,000 miles before failure. My advice to you would be to join the North American Norton Owners club and see how your engine numbers match up with known import batches . It could be you are in the clear , but if not then I would certainly fit Boyer , discard the points and think in terms of a serious strip down in the not too distant future.

    It only has to be done the once and then you have a superb low mileage bike.

    A regards the sludge trap .. well opinions on that will vary ..

    But the noise you are currently worried about is nothing. though you should not let it tick over .
    blip the throttle when warming up so oil gets thrown up the bores by the flywheels.
     
  8. timmyC

    timmyC

    Joined:
    Jul 27, 2016
    Loud valves do save lives!! Product date was April 1972 and I am the 4th owner of the bike. The bike came from Alabama where the second owner lived and passed away. The last plate on the bike was 1978 or 79'. The third owner bought it from an estate sale in early 2016. I bought it in July of the same year. I was told it sat in a basement for all those years. The third owner changed fluids, replaced mufflers, tires and got it running. During my first ride I discovered a severe oil leak that appeared to be coming from the right side exhaust. I let it sit not having the time or place to work on until last weekend. I discovered that the oil line from the crankcase to the right side of the head had a small hole in it at the barb. I trimed it and pushed it back on, problem solved. I was amazed that it started up on the 5th or 6th kick after 2 years! I am aware of the main bearing problems that Norton had on the Combat engines. That is on the list to verify whether they have or have not been replaced. I was hoping to ride it cautiously for a while before I make it yet another project to complete. I am planning to join the NANO and the Michigan Norton Owners group to meet other Norton owners. Thanks for all the input and suggestions.
     
  9. eskasteve

    eskasteve VIP MEMBER

    Joined:
    Sep 24, 2012
    I've owned three Combats and once warmed up none of them clattered like yours. That's about 115,000 miles worth of experience. As stated previously your best plan of action is to get an experienced ear to have a listen first hand. One of the oddest bad noise generators turned out to be the rear brake light switch mounting plate being impacted by the primary case. It dug a dandy gouge in the primary
     
  10. motorson

    motorson VIP MEMBER

    Joined:
    Nov 29, 2011
    I bought a combat with only 2000 miles on it and rode it for about a thousand or more before overhauling the engine. I did the superblend crank bearings and changed the pistons. Yours will have the teardrop pistons which would allow the entire skirt to fall off in the crankcase if it is ridden up to Combat performance levels. Any way, mine never did and a lot of others have used those pistons for a lot of miles with no incident. The noise sounds normal to me for all the reasons others listed. I think I could hear a bit of piston slap too so if it was cold that would explain that noise. I say, if the compression is good and you've confirmed oil to the head then ride it! But, keep your fist out of it like you said you would and avoid the temptation to wring it out like a Combat.
     

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