Announcement

Collapse
No announcement yet.

Mikuni VM34 Carbs

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
  • #1

    Mikuni VM34 Carbs

    Has anyone tried a modern replacement for our carbs like a set of VM34's? I see Mikuni VM's on all sorts of bikes nowadays that are being rebuilt, especially for those models that stock carb parts are impossible to find. I'm assuming they'd have to be jetted appropriately for our bikes which would take some tuning but with a brand new carb body replacement parts would be much easier and cheaper to find.

    http://www.amazon.com/Mikuni-Round-S...s=mikuni+carbs

    http://www.amazon.com/Mikuni-Rubber-...xgy_auto_img_y

    I was thinking about getting a set of 4 of these and they even come with a matching set of carb boots! For ~$400 I think that it may very well be worth the investment.
    78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
    79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


    "May my tires not fail me, nor my engine grow cold"
    Tags: None
  • #2
    Originally posted by D0wn5h1ft View Post
    Has anyone tried a modern replacement for our carbs like a set of VM34's? I see Mikuni VM's on all sorts of bikes nowadays that are being rebuilt, especially for those models that stock carb parts are impossible to find. I'm assuming they'd have to be jetted appropriately for our bikes which would take some tuning but with a brand new carb body replacement parts would be much easier and cheaper to find.

    http://www.amazon.com/Mikuni-Round-S...s=mikuni+carbs

    http://www.amazon.com/Mikuni-Rubber-...xgy_auto_img_y

    I was thinking about getting a set of 4 of these and they even come with a matching set of carb boots! For ~$400 I think that it may very well be worth the investment.
    Parts for the OEM cv carbs aren't difficult to find though....
    XS1100F 1980 European model. Standard. Dyna coils. Iridium plugs. XS750 final drive (sometimes). Micron fork brace. Progressive front springs. Geezer regulator/rectifier. Stainless 4 into 2 exhaust. Auto CCT (Venturer 1300) SOLD. New project now on the go. 1980 European model.

    Comment

    • #3
      Originally posted by James England View Post
      Parts for the OEM cv carbs aren't difficult to find though....
      I guess but I'm speaking more to the general condition of these old, out of production carbs. Diaphragms are very expensive, carb boots are $100, broken float posts, broken off idle mixture screws, leaky throttle shafts...the list goes on. I'd really like to see if there's a way to update the 30 year old carb system without going fuel injection.
      78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
      79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


      "May my tires not fail me, nor my engine grow cold"

      Comment

      • #4
        Originally posted by D0wn5h1ft View Post
        Has anyone tried a modern replacement for our carbs like a set of VM34's? I see Mikuni VM's on all sorts of bikes nowadays that are being rebuilt, especially for those models that stock carb parts are impossible to find. I'm assuming they'd have to be jetted appropriately for our bikes which would take some tuning but with a brand new carb body replacement parts would be much easier and cheaper to find.

        http://www.amazon.com/Mikuni-Round-S...s=mikuni+carbs

        http://www.amazon.com/Mikuni-Rubber-...xgy_auto_img_y

        I was thinking about getting a set of 4 of these and they even come with a matching set of carb boots! For ~$400 I think that it may very well be worth the investment.
        Manual slides and 4into1 'gang' cable...........would'nt say that's exactly modern.
        81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

        Comment

        • #5
          Originally posted by motoman View Post
          Manual slides and 4into1 'gang' cable...........would'nt say that's exactly modern.
          Yeah...I might getting stupid again. It just seems like there are so many other replacement carbs for other motorcycles beside the OEM ones. I've read about people using flat-side but that sounds like overkill. The obvious answer here to "update" the fuel system is to attempt fuel injection but I'm not prepared to go gray over something like that.
          78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
          79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


          "May my tires not fail me, nor my engine grow cold"

          Comment

          • #6
            There's multiple reasons why those would be a poor choice.... the two biggies are...

            First, you'll need four throttle cables; one to each carb. These carbs don't have throttle shafts/butterflies, instead the slide has to be mechanically lifted for throttle opening. So you'll need some sort of 4-to-1 cable adaptor to connect to the hand throttle, plus a length adjustment at each carb cable for carb syncing. I've seen these installed in two-carb setups, but never four, so this will all be custom.

            Second, these aren't CV-type carbs. These are a throwback design, best suited to dirt bikes or racing where the throttle is usually either open or closed. You'll have a terrible flat spot at most sudden throttle openings, maybe big enough at off-idle that the bike will just die. A CV carb will only allow whatever amount of air it needs into the motor according to demand (engine vacuum), on these it's all mechanical. To help eliminate the stumble, you need an accelerator pump on the carb which these lack.

            This type carb was commonly used in the 50s through to the 70s, but disappeared on most bikes because of both performance and emissions reasons.
            Fast, Cheap, Reliable... Pick any two

            '78E original owner - resto project
            '78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
            '82 XJ rebuild project
            '80SG restified, red SOLD
            '79F parts...
            '81H more parts...

            Other current bikes:
            '93 XL1200 Anniversary Sportster 85RWHP
            '86 XL883/1200 Chopper
            '82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
            Cage: '13 Mustang GT/CS with a few 'custom' touches
            Yep, can't leave nuthin' alone...

            Comment

            • #7
              For civilised road use, CV carbs are best and easy to use, flatslides are noisy at low openings and a bit of a handful. Not suitable IMHO for anything other than track. I considered then for the XJR and dropped the idea after a bit of research and advice. A refurb of OEM cv carbs is easy to do and diaphragms have dropped in price recently.. I did a set and transformed them to solid, reliable carbs.
              XS1100F 1980 European model. Standard. Dyna coils. Iridium plugs. XS750 final drive (sometimes). Micron fork brace. Progressive front springs. Geezer regulator/rectifier. Stainless 4 into 2 exhaust. Auto CCT (Venturer 1300) SOLD. New project now on the go. 1980 European model.

              Comment

              • #8
                I would try the FJ or Zrx carbs if upgrading, all parts will still be available for those styles and the spacing should be correct.
                2H7 (79)
                3H3

                "If it ain't broke, modify it"

                ☮

                Comment

                • #9
                  I've never tried them on a 4 cylinder bike but have a pair on my CB72 sprint bike, they work great without flatspots and pull from tickover with huge torque all the way to red line.

                  I'm not sure but think the first CB750's used these type with a cable splitter similar to mine but with 4 outlet cables rather than my 2.

                  As said, the carbs are difficult to keep in sync, I considered 4 flatslides for my XS but was thinking of linking them with a lifter rail above and one cable
                  http://www.ebay.co.uk/itm/Mikuni-TM3...item3cd38966ed
                  Tom
                  1982 5K7 Sport, restored to original from a wreck
                  1978 2H9 (E), my original XS11, mostly original
                  1980 2H9 monoshocked (avatar pic)http://i145.photobucket.com/albums/r...psf30aa1c8.jpg
                  1982 XJ1100, waiting resto to original

                  Comment

                  • #10
                    Went searching again and found some round slides:

                    http://www.motorcyclecarbs.com/CARBU..._P9194C652.cfm

                    It seems like these would work just fine and $800 isn't too steep for brand new carbs.
                    78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
                    79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


                    "May my tires not fail me, nor my engine grow cold"

                    Comment

                    • #11
                      Or....these flatsides:

                      http://www.dynoman.net/carb/mikuniRS2.html

                      What would be better roundslides or flatsides?
                      78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
                      79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


                      "May my tires not fail me, nor my engine grow cold"

                      Comment

                      • #12
                        Originally posted by D0wn5h1ft View Post
                        Or....these flatsides:

                        http://www.dynoman.net/carb/mikuniRS2.html

                        What would be better roundslides or flatsides?
                        Neither, unless the bike is gonna spend all its time at the '1320'.
                        81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

                        Comment

                        • #13
                          Originally posted by motoman View Post
                          Neither, unless the bike is gonna spend all its time at the '1320'.
                          This guy doesn't sound like he had a terrible time with them:

                          http://www.xs11.com/forum/showthread.php?t=18237
                          78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
                          79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


                          "May my tires not fail me, nor my engine grow cold"

                          Comment

                          Previous template Next
                          Working...
                          X