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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 11, 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.
     
  11. timmyC

    timmyC

    Joined:
    Jul 27, 2016
    Quick update on the noise. I trailered the bike to a local Norton mechanic for a evaluation. We started it up and I am happy to report that it makes all the right sounds. He started his own 72 combat and an 850 that he had in the shop for a comparison. I am going to replace the throttle cable, plugs and tune the carbs today and go for a ride! Thanks for all your input and support!
     
    SteveA likes this.
  12. timmyC

    timmyC

    Joined:
    Jul 27, 2016
    Sorry one more thing. When I removed the the air filter to work on the carbs the element was saturated with oil. It appears that oil came from the breather on the oil tank, is this normal?
    Thx!
     
  13. tomspro

    tomspro VIP MEMBER

    Joined:
    Jan 25, 2014
    remove the hose from the airbox and run to a catchcan. then get a comstock crankcase reed valve. one less oil dump problem after installed.
     
  14. alan hodge

    alan hodge VIP MEMBER

    Joined:
    Oct 10, 2017
    old austin healy mechanic once told me...'valves are like farts i would rather hear them than smell them (burning).'
     
    cliffa likes this.
  15. maylar

    maylar

    Joined:
    May 13, 2007

    That's a common result of having overfilled the oil tank. When parked, some oil will migrate from the tank to the crankcases and make it appear that your oil level is low. It's called "wet sumping". You top up the oil level, then after the engine is started the oil in the cases returns to the tank and overflows into your air cleaner through the breather hose. Some people take extraordinary steps to mitigate wet sumping, but it's a condition that was known by the factory. The Norton rider's manual even says to run the engine for a couple minutes before checking the oil level.
     
  16. eskasteve

    eskasteve VIP MEMBER

    Joined:
    Sep 24, 2012
    Overfilling of the oil tank is one cause. I fill my tank to about the halfway point. Others fill only to the low mark. Every bike is different. A small catch bottle shoved in front of the battery is a great place to collect excess breather drippings rather than letting it ooze into the airbox. There are many available products to help reduce crankcase pressure to cut down on oil vapor in the breather line. Mitey-Mite vacuum breakers work well for very limited money. $5 at my local auto supplier. I put in a reed valved breather from Mike's XS for around $18. It seems to do the job plus looks cool. I have no experience with the Comstock breather but most users swear by them rather than at them. Another thing to look at is your oil line and crankcase breather routing. http://www.oldbritts.com/oillines.html has a great diagram of how all of those hoses should be run. The previous owner of my current bike had reverse connected the oil breather and the crankcase breather hoses at the tank. Worked OK but excessive oil spewage was concerning. I grabbed a beer and the Old Britts diagram and saw the problem. I owned the bike for about 500 miles before I solved this easy cluster fluck. It's times like this that makes me suspect that my brain was wired by Ol' Joe Lucas himself.
     
  17. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    On my 850, I get a metallic, scraping sound like I hear on your video if my primary case bit is a little too tight...apparently this distorts the casing enough to create scuff with one of the internal rotating items....so run that nut on loose side, use locktite to hold it on. Don't try to stop leaks at primary cover by over tightening..
    Answer is to seal it with silicone sealant.

    Also, my bike really quites down just under 1000 rpm....but it does a lot of shaking, esp front wheel and forks.
     
  18. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    If you look at the back of your chain case you will see where the centre mounting stud comes through
    This absolutely must be shimmed to the back of your chain case
    Try slackening off the chain case bolt and see if a gap appears
     
  19. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Thx...so shimming is between the stud and the inner casing? I have not yet tried to remove the inner chain casing...not sure what specialty tools are needed to remove the primary sprocket/clutch cage etc.
     
  20. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    You should not hear any noise when you tighten the centre bolt up
    The fact that you do makes me wonder if it's been shimmed properly,
    When the inner chain case is fitted you fit the chain case - crankcase gasket then the chain case then you nip up the 3 chain case mounting bolts and check the central mounting stud abuts to the back of the chain case
    If it doesn't then you add or subtract washers until it does ,
    I suspect yours could be missing some washers !
    Hence when you tighten the centre bolt the case could be bending inwards and making something touch?
    You can only speculate from thousands of miles away
    Also the 3 mounting bolts should have the tab washers re fitted (new ones) if you do ever take it apart..
    Personally I would undo the centre bolt and take a look at the back of the case
    If you can see a gap find a washer /washers that are the same thickness as the gap
    Cut the side of the washer out and slide it in, maybe with a dab of silicon to hold it in place and then tighten the centre bolt up
    Cheers
     
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