1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Noob question. 750 commando

Discussion in 'Norton Commando Motorcycles (Classic)' started by Doc187, Mar 17, 2019.

  1. Doc187


    Oct 14, 2018
    I fired up my new to me 750 commando for the first time on my own since having the top end rebuilt. It's loud and vibrates, A LOT! Is that normal?
  2. baz

    baz VIP MEMBER

    May 26, 2010
    Yes they are loud from the exhaust and maybe loud mechanically depending on what you are used to?
    They vibrate a bit on tickover but should smooth right out as you rev them this depends on how the isolastics are set
    But by 2500 rpm it should be smooth
  3. eskasteve

    eskasteve VIP MEMBER

    Sep 24, 2012
    If it's a Combat they do have more mechanical clatter when cold due to the greater valve lash. Have a local Norton owner give it an ear.
    Chicago Norton Owners Club

    Bill Walters, President
    P.O. Box 88411
    Carol Stream, Illinois 60188
    Doc187 likes this.
  4. rvich

    rvich VIP MEMBER

    Jul 25, 2009
    These things sound like a sewing machine, except for that wonderful exhaust note. Check your valve clearances. The chains in the timing chest and primary transmission can be noisy as well. Making sure they are properly adjusted is important but they won't be silent. A lose timing chain seems to make the whole valve train noisier. Regardless, the sewing machine sound is part of the experience.

    In the first video below, go in about 45 seconds and you can listen to the bike at idle.

    Or in this video you can listen at the beginning when the bike is first started. They will both give you a reference.

    Doc187 likes this.
  5. DogT


    Jan 20, 2009
    Mine always clatters a bit from the timing chain on startup, but after about a half mile it sounds more like the sewing machine. I can always hear the valve noises, especially gearing down around the corners, I've grown to like it. It's disconcerting if you're used to modern bikes.

    The vibration should get minimal at about 2500rpm and up. If you install the later style engine spring it will reduce the idle vibration a lot but I don't find it doesn't do much at speed.

    Don't tighten that primary chain too much or you risk bending the trans shaft and it makes for hard shifting. A bit loose is better than tight. The riders manual has an excellent and proper method of tensioning the primary, it's not very intuitive until you do it for a while and understand what it's doing.

    If you're not doing these things you should learn. It's part of the Norton mystique.
  6. grandpaul

    grandpaul VIP MEMBER

    Jan 15, 2008
    One man's "sewing machine" is another man's "coal train".

    They are pushrod operated, air cooled, chain driven, and make sounds.

    It's all about hearing other people's Commandos, and you pretty quickly learn what's "fine" and what's "uh-oh..."
  7. illf8ed


    Dec 30, 2003
    There is shake as when the front wheel is jumping up and down at idle and vibration is what you feel at the handlebars and foot pegs. Shake is normal. Too much vibration is not normal and usually caused my mis adjusted isolastics.
    Doc187 likes this.
  8. frankdamp


    Oct 7, 2005
    It's disappointing to me that the original VERY smooth running of the Commando prototypes was compromised by later development. There was very slight vibration at low idle speed (>1000 rpm) and absolutely none felt by the rider above about 1250 rpm. I never got to ride a production Commando as I was in the Wolverhampton development location and we rarely saw any.

    My regular rides, once the Commando went into production, were a US-built 750 cc desert racer and the prototype AJS Stormer. The desert racer was based on an Atlas engine in a Matchless frame and we got it for testing in advance of an accidental death lawsuit that was later dropped. I did the break-in riding on it for about 1500 miles. It later emerged as a Plumstead production model, the P-11. I think it appeared on the market about a year after I emigrated in early July 1968. On a visit to Marston Road after I emigrated, I saw the US-built desert racer and the Stormer prototype slowly rusting away in what had been the experimental shop. The company was in the early stages of preparing for dissolution. A very saddening visit.
  9. alan hodge

    alan hodge

    Oct 10, 2017
    i have 200 miles on my commando since project completion... and am still learnings its feels and sounds ... compared to the 1968 BSA A65 I have the Norton is decidedly quieter and smoother but still has a bit of very light clatter in 3rd gear at 3000 rpm other wise quiet...my 72 Triumph T120 has a lot of valve noise too but I have them set a little bit loose...also the Norton has some engine induced vibes at low rpm on center stand but none on the road....it's all like getting used to a new girlfriend and her 'quirks'
  10. jbruney


    Jan 5, 2019
    I notice the vibration after riding the highway and slowing to ride in town. Otherwise I'd not notice at all because everything is just so smooth from 2.5k up. 3k and there's only the wind....I can always hear it though...just like an old Kelvin st8.
  11. Doc187


    Oct 14, 2018
    Some things need tightening up like properly mounting the gas tank and rear fender. Three starts and a mile or two later and the right exhaust header nut is completely loose. I will also have a look at the iso settings. Fun times
  12. DogT


    Jan 20, 2009
    I remember my 70 S was smooth as silk when I got it in 72. New iso rubbers really aren't like the originals. But then they prolly handle a bit better, not that I could tell.
  13. htown16


    Apr 29, 2009
    A slightly loose gas tank can make a heck of a racket, especially when getting towards empty. Make sure you have the correct rubber pads beneath it as shown in the parts manual. Small rectangular one lengthwise in front and thicker square one in the rear.
  14. Matt Spencer

    Matt Spencer

    Jul 25, 2010
    It might shake , but it shouldnt rattle and roll .

    Should come turbine smooth at around 2.0000 rpm . Give or take a zero or two .

    Ex Haust knuts - you need the proper tool ( Make One . ) and LEAN on it , When the injuns HOT .
    After about four efforts ( seperate heat cycles ) the widdle copper washers are flattened , and if the pipes are aligned ,
    itll stay tight .
    If theyre Not Aligned , itll likely tear the stud thingos in the mufflers out .

    If the Iso's are over 5 thou . , itll roll & weave .At Speed . 2 1/2 is as tight as Id run em . To 4 1/2 .
    If the mounts are straight & alls square . Otherwise any binding transmitts the shakes .
    There should be NO BINDING in the mechanism .

    Keep it below 90 in third gear . Tho 23 T will give 112 odd . :cool:
    Doc187 likes this.
  15. gortnipper

    gortnipper VIP MEMBER

    Nov 11, 2013
  16. Fast Eddie

    Fast Eddie VIP MEMBER

    Oct 4, 2013
    Labouring the engine isn’t good for it you know...
  17. Deckard


    Jun 18, 2009
    the front wheel bounces at idle, you rev it on the center stand and it shakes and moves backwards. Norton owners entertainment for the masses.
  18. eskasteve

    eskasteve VIP MEMBER

    Sep 24, 2012
    I met my wife at a dance waaay back in 1973. The next day was our first date. I showed up at her house on my purple metal flake Combat not knowing if her parents would allow a sweet 17 year old girl to hop aboard for her inaugural ride. Thankfully they were in bed as they both worked nights. Away we went for a nice tour of Washington State's Whidbey Island. We stopped at South Whidbey State Park and had a picnic lunch of fire roasted hotdogs and generic cola. She must have enjoyed it as not only are we still together 46 years later, but we still do a lot of riding though not too much on the Norton as it seems to have shrunk over the years. Today I asked her what she liked about that first ride. I expected to hear something about how well I handled the bike, the lean no frills approach to motorcycling that Norton embraced, or even something concerning my rugged swarthy good looks. Nope. She liked the subtle low speed vibration. She found the sensation "interesting". 46 years of false self delusion on my part. Hmm. Shake, rattle, bounce, and roll you bad boy mechanical vibrator. Once you're confident that all is well with your new ride look for someone to share the experience with. Giddyup!
    Last edited: Mar 21, 2019
    Tornado, rvich, tomspro and 2 others like this.
  19. Craig

    Craig VIP MEMBER

    Dec 20, 2005
    I met my wife in ‘76 at a Legion dance , I had just tried jumping on table without spilling rugby club’s drinks and failed ... she came out of the crowd and asked to dance and saved me .... years later she said if she had seen the table jump she would have asked some one else .... she never rides with me ever , my need for danger is still alive and well , eh ..... the Norton runs very smooth as it should .... and no drips ...
    Tornado likes this.
  20. eskasteve

    eskasteve VIP MEMBER

    Sep 24, 2012
    Why is it that women worth having just don't seem to understand or appreciate a man's attempt to achieve greatness? Table jumps, hands free tequila shots, beer drinking challenges, long motorcycle rides to nowhere, etc. Relationship mysteries just like the mysteries of what's a normal sound for a Norton.
    Craig and Tony Pierce like this.

Share This Page