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Keihin CVK Carb Conversion

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    Keihin CVK Carb Conversion

    I’ve just started adapting a couple of Keihin CVK carburettors for my 760 Bros (XRV750 engine). They are from a bank of four, off a Kawasaki ZX7R, I think. The bore size is around 38.6mm which perhaps makes them nominally 39mm?

    It would be great to hear from anyone else who has done similar - there’s various technical problems to solve and obviously the jetting eventually.

    The main technical problems I’ve noted so far are:

    Making a second throttle pulley. I’m going to run two separate cables to a twin pull Domino throttle
    Adapting the cold start mechanism to the usual NT650 arrangement.
    Finding a suitable metal fuel inlet elbow to press in, replacing the plastic pipes usually connecting the carbs in the standard bank set up.
    Tidying up the air intake side. I currently have open carbs with bellmouths with a bit of gauze to stop anything big going down there - I’ll probably try to rig up something similar.

    I’ve made a start and have the carbs on a spare motor shell and have been machining the cold start plungers to accept cables.

    #2
    PoorMansFlatslides. These are the ones the racers used to use....CV40's from a 92-94? KZ or ZX1000 Kawi (don't recall)


    you buy 2 banks.....use the masters.....plug the vac stuff and create a double throttle.....sync by ear....use the standard rubber stacks....or use them to mount pods...(coarse snomobile pods in pic)
    jetting is easy......use the stock pilot and 160/165 just like a Hawk700 engine.

    lotsa work and only pays off over 75hp or so..... mikebike 003.JPG mikebike 005.JPG mikebike 004.JPG

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      #3
      These accepted the stock choke cables IIRC......ask Goshawk.He knows this stuff...this is one of his with the 40's.. pete 005.JPG

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        #4


        ​​​​​​​
        I’ve made a start! The two cold start things that I’ve cut down, turned on the lathe and drilled/milled for the cable are next to the standard NT650 one.

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          #5
          Originally Posted by behindthetimes View Post
          PoorMansFlatslides. These are the ones the racers used to use....CV40's from a 92-94? KZ or ZX1000 Kawi (don't recall)


          you buy 2 banks.....use the masters.....plug the vac stuff and create a double throttle.....sync by ear....use the standard rubber stacks....or use them to mount pods...(coarse snomobile pods in pic)
          jetting is easy......use the stock pilot and 160/165 just like a Hawk700 engine.

          lotsa work and only pays off over 75hp or so]
          Poor man - that describes me… I like the proper flatslides but its a heap of money.

          I’m intending to do it with one bank, making a suitable pulley to go on one of the other carbs. All the carbs have the same cast in mounting points so I can drill and tap these for the cable adjuster, and the tick-over screw.

          Thanks for the comments and the jetting suggestion - I’ll use that as a starting point when I get that far.

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            #6
            You seem like a mover and a shaker.....you'll get er done.

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              #7
              Pingel makes a nice billet dual throttle assembly for the HD drag bikes.........but the cables will need to be fabbed.

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                #8
                Originally Posted by behindthetimes View Post
                Pingel makes a nice billet dual throttle assembly for the HD drag bikes.........but the cables will need to be fabbed.
                That Pingel stuff isn’t cheap… I looked at their fuel taps for a while but in the end rebuilt and tarted up the stock one.

                The twist grip I got is an Italian one - apparently similar to the Yam TZ one. It wasn’t cheap either for a simple bit of aluminium and plastic. There doesn’t seem much else available if you want to avoid using a splitter box.

                DA9ECB99-A128-4656-B06A-78BB60B23754.jpeg

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                  #9
                  CC47B079-3811-49EF-AA42-D38C94080617.jpeg I’ve been making a couple of fuel inlets to press in and also various blanking plugs.

                  37C9DB23-4BC8-4B02-9249-8C84152DF8F4.jpeg
                  Last edited by DrPMC; 07-24-2021, 02:35 PM.

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                    #10
                    Originally Posted by DrPMC View Post
                    CC47B079-3811-49EF-AA42-D38C94080617.jpeg I’ve been making a couple of fuel inlets to press in and also various blanking plugs.

                    37C9DB23-4BC8-4B02-9249-8C84152DF8F4.jpeg
                    Nice combo of salvage and creativity? Or did you brew that all from scratch?Either way....clever work.

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                      #11
                      Originally Posted by DrPMC View Post

                      That Pingel stuff isn’t cheap… I looked at their fuel taps for a while but in the end rebuilt and tarted up the stock one.

                      The twist grip I got is an Italian one - apparently similar to the Yam TZ one. It wasn’t cheap either for a simple bit of aluminium and plastic. There doesn’t seem much else available if you want to avoid using a splitter box.

                      DA9ECB99-A128-4656-B06A-78BB60B23754.jpeg
                      Double pull or a Push/pull that needs an inner wheel? Looks nice.

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                        #12
                        not worth the effort or expense compared with stock carbs. wadda u gonna get, 2-3 hp and trouble getting jetting right ? maybe ok on a race bike, not so good on the road.
                        Last edited by squirrelman; 07-24-2021, 06:50 PM.
                        "It's only getting worse."


                        MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

                        Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

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                          #13
                          Originally Posted by behindthetimes View Post

                          Double pull or a Push/pull that needs an inner wheel? Looks nice.
                          Its a double pull item.

                          Comment


                            #14
                            Originally Posted by squirrelman View Post
                            not worth the effort or expense compared with stock carbs. wadda u gonna get, 2-3 hp and trouble getting jetting right ? maybe ok on a race bike, not so good on the road.
                            I suppose that the sensible thing would be to get a SV650 or perhaps a nice little car?

                            This carb type is used by Honda on the last versions of the XRV750. It’s 2mm up on the stock bore which is usually seen as a good choice for a motor like mine - higher comp, 760cc, free flowing at both ends, stage 1 type gas flow.

                            If it doesn’t work out I can just pop the stock items back on.
                            Last edited by DrPMC; 07-25-2021, 02:10 AM.

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                              #15
                              It's the idea of all the work that bothers Squirrel. Shit.....just use a piece of steel plumbing strap for a fuel pump mount...then you'll be able to relate.
                              760cc? AT engine? ....with all his fiddling Hord said the stock carbs would support about 75 hp.Depending on your state of tune this could be a couple ponies.
                              Any dyno work on your engine?
                              Last edited by behindthetimes; 07-25-2021, 06:43 AM.

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