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Twin choke weber

Discussion in 'Norton Commando Motorcycles (Classic)' started by pommie john, Nov 18, 2005.

  1. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    Does anyone know where I could buy a manifold to fit a twin choke weber carburetor to my 750 Commando?

    I've seen it on a couple of bikes and it seems like a good project.
     
  2. huub

    huub

    Joined:
    Dec 4, 2005
  3. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    Thanks for that. It looks like I might have to make the emanifold myself, but when it's done that will be very useful.
    I'm suprised they use a 30mm venturi for a 750. I would have expected 32 -34mm.
     
  4. Blkbird

    Blkbird

    Joined:
    Aug 18, 2005
    Actually the weber I have had its manifold machined to fit the Norton can't recall now what size weber. sitting in gunk now but I might pull it out for a couple of pics if it would help
     
  5. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    I'd be very interested to see it. Also, do you know what the manifold originally came off?
    I've been looking around and think maybe a Nissan 6 cylinder one may be modified to fit...and I'd get three goes at getting it right.
     
  6. Blkbird

    Blkbird

    Joined:
    Aug 18, 2005
    Actually this one was entirely machined at a machine shop from a block of aluminium some 20 years ago from what I've been told from the old owner (amazing the $h*t you do when you are a teen). Too darn cold to go play in the garage right now but I promise I will get some pics
     
  7. MichaelB

    MichaelB VIP MEMBER

    Joined:
    Jan 14, 2004
    We do take life for granted here in SoCal.
     
  8. Blkbird

    Blkbird

    Joined:
    Aug 18, 2005
  9. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    Thanks for that, it's much appreciated.

    I would love for a bit of cool weather...it's mid thirties with high humidity here in Brisbane, I'm sweating onto the keyboard.
     
  10. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    Oh yeah...do you want to sell it?
     
  11. Blkbird

    Blkbird

    Joined:
    Aug 18, 2005
    The only way I would consider selling it is has a package. Weber and manifold together
    regards
     
  12. pommie john

    pommie john

    Joined:
    Nov 18, 2005
    OK, thanks, but I've already got the Weber.

    Thanks for digging it out and photographing it.

    Maybe I'll start a new topic when it's up and running.

    John
     
  13. prmurat

    prmurat

    Joined:
    Jun 6, 2003
    Nice manifolds!!! I'd love to do this on one Atlas Hybrid I have (Matchless G15), hoping it will look better than the Mikuni (for a Commando) it came with. Do you have any picture of your bike with the Weber?
    Tks
    Phil
     
  14. Blkbird

    Blkbird

    Joined:
    Aug 18, 2005
    Sorry I hadn't read threads in a while since it's cold up here in the Great White North-Canada :lol: and that places me in motorcycle mourning season. No pics with the Weber carb and manifold combination installed. I actually went with a set of Wal Philips fuel injectors :twisted:
    for this rebuild as the 2 bikes came in boxes and was a ground up. Thought it'd look cooler on a 810 kit
     
  15. prmurat

    prmurat

    Joined:
    Jun 6, 2003
    Any news on this Weber installation? Photos?
    Philippe
     
  16. Chris

    Chris VIP MEMBER

    Joined:
    Jan 21, 2008
    Hi Pommie John
    Sold my manifold to an Aussie last year!! My mate John runs one on his Atlas sprint bike I will get some photos. He has just about sorted out all the various jets etc.
    all the best Chris
     
  17. ML

    ML

    Joined:
    Jul 30, 2007
    John,
    Having custom made my manifold for a Vm34 Mikuni and fitted several other "'off the shelf'" manifolds to Commandos, I can say there are potential difficulties with clearance around the rear frame junction and choice of appropriate airfilters and keeping adequate tuned inlet length.

    Going to a Weber is a whole new exercise, and I think a bloody good idea. All the benefits of twin choke and none of the vices of the Concentrics. OK, let me say this in my defence from the purists - the Weber has immense tuning options and wears very little. The Amal doesn't.

    I'd suggest working out the manifold dimesions and spatial fitment with modeling balsa wood from your local hobby store. It comes in convenient shapes and sizes and is easy to work with. Rough it out to fit and you've then got a pretty reliable reference to fabricate the real thing.

    If you get it done, I sure we'd all like to hear how well it performs. And if its winner, I'm up for one as well....

    Mick
     
  18. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    Before I got EFI I ran a DCOE for nearly 10 years on my Commando. It required removing nearly all of the web at the down tubes and was still a very tight fit. It also required a rear mount for the carb as the manifold to head bolts would not support the heavy carb on a vibrating engine without either breaking the bolts or the manifold. The carb mount was a strut down to the rear of the cradle over the transmission. A fuel pump was required because even with a huge alchohol inlet needle and seat ,gravity would not keep the vibrating carb full of fuel. I used a vacuum pulse pump for some time and then went to a tiny rotary electric that I used for several years. I built a fiberglass air box with a single K&N filter attached. Getting the carb installed was a large winter long project and getting the jetting spot on was a year long ordeal.
    With all the sacrifices made in the porting and intake lengths just to make it fit the power was on par with a set of stock carbs. Not as good as a pair of Keihins or Mikunis. The drivability and starting was very good once it was fine tuned. Working on it was a real pain.
    I would never do it again. Jim
     
  19. willh

    willh

    Joined:
    Feb 3, 2010
    I wanted to do this about 10 years ago and was talked out of it for all the same reasons. I still consider doing it though,if for no other reason than I like the look and idea of running a single 2 barrel side draft carb. It would fit the frame well on my current project.
     
  20. Seeley920

    Seeley920

    Joined:
    Jan 6, 2009
    I know John was running his Commando in a featherbed, so space is less of an issue...I also know someone who used to racea Seeley commando with a Weber, and also a guy who used one on his Weslake. All are now running Amal Mk2 Smoothbores!!!
     

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