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O/T 4 cyl honda, 4 carbs, someone ?

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  • O/T 4 cyl honda, 4 carbs, someone ?

    i have just got my "new" 84 honda 700 with v-4 & 4 carbs and it has some problems. is there any of you guys out their that have ANY experience with these and their carb problems ? private email as i have a bunch of questions about the carbs. . . . . don't know where else to ask.

    davidh tooldoc at cheqnet dot net. . . . . or even a phone call; ; ; ; ;

    seven one five, three six three 2404

  • #2
    I have breathed life back into a lot of old motorcycles. Carbs are a major problem, parts are criminally expensive. Some carbs are a nightmare to remove.
    A friend brought me a 1983 V45 Honda that had been sitting for years gas poured out of the carbs when he tried to start it. I drained the carbs and lifted the tank and removed the vacuum slides Then I filled the carbs with "gunk" brand "carb medic" and drained them again several times over the period of a week, the first time the stuff that came out of the drains was green slime after a few days the "carb Medic" came out clear. I put fresh gas in the tank and it fired up and ran great. It's still running years later.
    It's wotrh a try.

    Terry

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    • #3
      Also look for a product called power tune, can be found at marine parts supply's. Drain gas from carb via drains in float bowls and pull fuel lines. Spray power tune down fuel line till foam comes out all vent lines and let sit for and hour. Repeat and then drain and fill with fresh gas.

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      • #4
        An ulrasonic tank is your friend when cleaning carbs. I have access to a 10 litre one at work that cost a lot of money, but there are some pretty cheap ones around now.
        Paul Compton
        www.morini-mania.co.uk
        http://www.youtube.com/user/EVguru

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        • #5
          Some more specific info on the problems might yield better suggestions. What's happening?

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          • #6
            If it has been sitting for more than 6 months a pilot jet or pilot jets are plugged. The pilot jets control the idle circuit. If they are all plugged the engine will only run on the enrichment circuit, if it's only one it will start and idle but not very well. I have seen some pretty dirty carbs but rarely have I seen one where the main jet is plugged.
            The carbs would need to be removed and the float covers taken off. Under the cover is a boss in the casting that has the pilot jet screwed into it. Use a screwdriver that fits the slot perfectly. Some pilots are quite tight and if you use a poor fitting screwdriver you could round out the slot. One they are removed you will need to soak them in carb cleaner for a day and then what I do is use a strand from a very fine wire brush and poke out the hole. It's small but you should be able to see light through it.
            gbritnell

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            • #7
              thanks so very much. i believe mr britnell haspretty much described the problem and hopefully the solution. idle speed at 2000 plus, starts and runs great at rpms that are higher than that. when shifting, rpms actually increase before they decrease at each shift.

              two of the springs that are suppose to help the plungers return were in the wrong carbs and i would think that itself would be a goodly part of the problem.

              after work i will turn the assembly over and open up the float bowls and pull and soak jets as suggested.

              diaphram kits, +-130, carb gaskets +- 30 for each carb, times 4 ? ? ? these old things are as bad as a . . . .

              going into detail about O/T stuff might piss some guys off so i didn't want to initally. . . but i will share the outcome. the season is coming to a quick close. 49 this morning, hi of only 70 expected. aaaahhhhh !

              thanks very much for the good advice.

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              • #8
                Those bikes are originally equipped with "CV" (constant velocity, or sometimes called constant vacuum) carburetors. Unlike "normal" carbs, the throttle opens a butterfly valve* instead of directly operating the slide. The slides are operated by rubber diaphragms contained in the top of the carb body. The diaphragms occassionaly develop vacuum leaks. That can cause some real head-scratching problems. As noted above, new diaphragms aren't cheap. You can test them easily with a vacuum hand-pump (like a Mity-Vac).

                * The throttle butterfly is on the downstream, or engine side of the carb. A butterfly on the air-filter side is the choke. BUT... they don't always have a choke butterfly. Some use a special circuit within the carb, usually operated by a push/pull lever or rod.

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                • #9
                  ALL the Nippon Moto Sickle manufacturers work on the TTBAABANO principle, they invented it.

                  Regards Ian
                  You might not like what I say,but that doesn't mean I'm wrong.

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                  • #10
                    it works !

                    thanks for the great info. it was a "no-parts" overhaul. . the beest kind.

                    the slides were sticky, a bit of real fine steel wool made them slide really great. one of the little idle jets was plugged, and it unplugged with just the pressure from the carb cleaner power.

                    a pain in the butt to re-assemble everything as it was apart for a week, "where did this go, where did that go" kinda thing. . . .but,

                    after a decent dose of starting fluid, it ran like a champ, the idle is at about 600,maybe a little slow even but it was a joy to ride it on a 2 mile maiden voyage around the township.

                    again, thanks for the great information. what a great bunch of guys. . . .

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                    • #11
                      I will give the advice a shot also. I have an 85 V65 Magna with the same problem. Hopefully, I can get it running again.

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                      • #12
                        I assume you mean the CB700? Yahoo has a few forums, the first seems to be the more active.

                        http://autos.groups.yahoo.com/group/honda_nighthawk/
                        http://autos.groups.yahoo.com/group/hondanighthawk700s/

                        Lots of knowledge specific to your machine on those forums, as well as some file downloads and links you may find interesting. Good luck & ride safe.

                        Jim

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