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CB750 rear wheel on 73 Commando ?

Discussion in 'Norton Commando Motorcycles (Classic)' started by bluto, Nov 30, 2018.

  1. bluto

    bluto

    Joined:
    Jul 15, 2010
    I'm unhappy with the cush drive, two piece axle, wobbly drum/sprocket etc. on my bike and rather than try to fix all that plan to swap in another wheel. Did see a reference here on people using CB750 wheels back in the day but there were no details...so if anyone knows more and/or has some thoughts on this would greatly appreciate hearing them.
    (I do know the sprocket and rim will need to be aligned to match the stock setup and that one or two custom spacers may be required along with a brake stay and custom cable)
     
  2. 84ok

    84ok

    Joined:
    Aug 10, 2014
    pretty sure grandpaul used a cb750 drum brake wheel on one of his bikes & one part was drilling a hole in the cradle for the torque arm/(stay?), not sure about the axle bits..

    beauty of that also is there were a ton of aftermarket mag wheel options including 16"
     
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  3. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    well, remember the brake is on the wrong side.much to consider , axle diameter,offsets etc. Here is another option,
    proper cush drive hub with one piece axle designed for original replacement. GEDC4495.JPG GEDC4497.JPG
     
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  4. KiwiNeill

    KiwiNeill

    Joined:
    Jul 25, 2011
    bluto
    I successfully fitted a CB750 K2 drum brake hub to my Atlas special in 1976 and it worked perfectly over 100,000+ miles, latest resto mod is changing it to the later CB750 disc brake hub using the Norton Lockheed calliper.

    This hub could be readily adapted to suit a Commando but non Mk3 models would need a custom cable or crossover rod arrangement and spacers as you say.
    A good range of JTR284 530 sprocket sizes are available including a standard Commando 42t which matches the Norton front sprocket and is lighter and £84.00 cheaper than the awful one piece Commando drum brake sprocket.
    Line up the rear sprocket centre to the front, calculate the wheel offset to the frame centre and have the rim respoked to match.
    I used a 3.00" x 18" Akront rim with the 20mm CB750 axle and welded a lug to the swingarm for the torque arm.
    The sprocket carrier may need machining to optimise the sprocket to hub centreline dimension of a Commando but someone here may have that info.
    I can measure the Honda sprocket to hub centre to give an initial datum if it helps.

    My Commando retains the lovely Mk3 conical disc hub with a Kawasaki GPZ500 -ER500 520 sprocket drive.
    I adapted this to the original Commando alloy cush drive centre and rubbers for cheap and easy sprocket changes while the thinner chain provided extra clearance to fit radial tyres.
    Not overly expensive but plenty of head scratching, hand fabrication and a good local machinist essential, a fit and forget mod that also works perfectly and looks like a factory fitment. The Norton front sprocket requires machining to 520 size 0.227" thick.
    DID 520 ERV3 X ring chain is fitted to a 42t JTR486 sprocket which is also used for 520 chain conversions on GSXR600, 750 and 1000cc models.

    A custom one piece axle with a single nut was fitted together with new spacers but the CB750 hub, axle and chain adjusters would be a much better option in your case as it uses existing 530 chain so standard front sprockets can be used.
     
    Last edited: Nov 30, 2018
    bluto likes this.
  5. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    You can't anchor a torque arm to the cradle unless you convert the brake plate to fully floating
    It'd be best to weld a lug onto the swing arm
     
  6. 84ok

    84ok

    Joined:
    Aug 10, 2014
  7. Klaus Monning

    Klaus Monning

    Joined:
    Nov 27, 2014
    Hello,
    I fitted a Suzuki GS 500/550 rear hub. That seems a lot lighter than any Honda hub, be it the CB 500 or 750 one. The disadvantage of the brake being on the wrong side is the same.
    I even kept the 2- piece axle, because if you want to dismantle the rear wheel there's no need to touch the chain. I think the old design wasn't all that bad. Only the sprocket/brake drum combination and the cush drive was a bit questionable.
    If someone wants a photo just drop me a PM.
    Best Regards
    Klaus
     
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  8. 84ok

    84ok

    Joined:
    Aug 10, 2014
  9. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
  10. 1973x75

    1973x75

    Joined:
    Nov 15, 2015
    Definitely consider the madass setup. I got one, and it was a perfectly easy swap. Now I have the original for garage art.
     
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  11. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    I would avoid the CB500/4 hub as the brake drum is thin on metal and has a reputation for cracking!!
    no idea about the 750 one.
     
  12. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Yes you are right about them cracking I'd forgotten about that, I think the 400 four cracked as well
     
  13. grandpaul

    grandpaul VIP MEMBER

    Joined:
    Jan 15, 2008
    My brake torque arm was anchored to the swingarm, NOT the cradle. I believe I used a clutch cable to near perfect effect for the loop-over.
     
  14. bluto

    bluto

    Joined:
    Jul 15, 2010
    Thanks very much to all, this info gets me on the right track and I'm going to try and make a Honda (or maybe Suzuki?) wheel work...but will go with the Madass setup if it doesn't (FWIW am using his front MC and am very happy with it), ideally I want a removable and easily sourced sprocket and may go 520 as well. I do weld and can modify cables so that should help. BTW in case others try this and/or need to fool with cables the Flanders instructions below were very helpful...and in my case I used a black iron pipe cap (securely clamped for safety) as a solder pot and a propane torch to melt the solder (which remains molten in the pot for quite awhile so no need to rush the job) Plumbers solder and flux worked OK for me.

    [​IMG]
     
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  15. 84ok

    84ok

    Joined:
    Aug 10, 2014
    honda axle? spacer(s)?
     
  16. grandpaul

    grandpaul VIP MEMBER

    Joined:
    Jan 15, 2008
    Home-made spacers with Honda axle. Note that it's a rare Kenny Dreer box-section swingarm, so I was able to slightly open the axle slots. Not sure how a standard swingarm slot would fit a Honda axle.
     
  17. o0norton0o

    o0norton0o

    Joined:
    Apr 27, 2015
    I mounted a yamaha cast wheel front and back on my commando, My set up looked like this below: You can see the homemade fat brake cable I made to go forward, then loop over the fender to the left side brake lever in this picture. I welded a tab on the swingarm for the drum brake torque arm which is hidden by the Z plate in the picture. The sprocket carrier face was machined down .25" to align the sprocket, the size of which is easily changable. In fact you can buy "saw cut" sprockets and change out to different rear sprockets sizes without removing the wheel.

    [​IMG]

    My cast wheel modification was not any cheaper than buying Madass's beautiful hub set up, except I did both front and back wheel conversions for about the price of his whole rear set up including 2 new alloy rims. The machinist costs to adapt the non-commando wheels raised the costs of my swap, pretty much eliminating any savings I thought I would have to adapt these wheels. Here's the front wheel pictured below.

    [​IMG]

    My story was: I needed new tires, but didn't want to keep the early commando non-cush hub, nor the skinny, steel WM2 rear rims. I went for the whole shootin' match. The rear set up is the yamaha wheel on a one piece 17mm yamaha axle in a commando swingarm slotted to 17mm.

    I've done a lot of research on this modification, and since I've done it I've seen even better wheels to adapt on craigslist or ebay which cost next to nothing. Some of those cast wheel sets are WM3 x 19 front rims , with WM4 x 18 rear rims which would be great for commandos IMO... I could look if you're interested and see if there's any good candidates available...
     
    Last edited: Dec 1, 2018
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  18. 84ok

    84ok

    Joined:
    Aug 10, 2014
    what year model yam?

    someone else went with rd400 mags
     
  19. o0norton0o

    o0norton0o

    Joined:
    Apr 27, 2015
    82 seca 550 in my case, but as I said there are even better choices that I discovered in later research.
     
  20. bluto

    bluto

    Joined:
    Jul 15, 2010
    Thanks, those photos help...at this point I'm planning to stick with spokes and swap out the rear wheel only, found a CB450 wheel locally in the meantime and am going to see if I can make it work.