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Is the fuel pump relay actually necessary?

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    Is the fuel pump relay actually necessary?

    I wonder if the fuel pump relay is actually mandatory?
    I believe mine doesn't work and it is very hard to find a new one where I live.

    I've noticed that once the relay shorted, the pump will work until the carbs are full, then it stops naturally by itself after it senses enough back pressure.
    So basically it doesn't need a relay to get on and off automagically, it does that just by itself.

    So I wonder, what is the actual purpose of this relay and can I just run the bike without it?

    #2
    It's supposed to be a safety feature to prevent a crashed bike from dumping fuel out because the key is still on.

    Many owners bypass it.

    If you were looking for a support group you're barking up the wrong tree. This place is fulla enablers dude. - Shooter77us

    The bitterness of low quality lingers long after the thrill of a low price has gone. - RacerX450

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      #3
      Ah yeah, that makes sense, thank you!
      I'll go for no safety then, and try to find a new relay in the meantime

      Thanks again for your help !

      Comment


        #4
        after the first time that bloody relay left me stranded, i've bypAssed it on every honda i've owed........and i ain't boined up yet so far.

        Last edited by squirrelman; 11-09-2022, 09:59 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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          #5
          I had mine bypassed and got into an accident. Gas spilled all over the ground but it wasn't really a problem. I have a vacuum pump now so it no longer matters anymore.
          Brian - Richland, WA
          1991 Hawk GT
          1997 VFR

          Comment


            #6
            Originally Posted by bk94si View Post
            I have a vacuum pump now so it no longer matters anymore.
            Seems interesting, could you tell me more about it or point me to a thread?
            I've got very limited confidence in my pump, it already broke once and I had to repair it with the remains of another pump, so I can't say I'm very confident for it to run for long...

            Comment


              #7
              Hordpower.com
              Brian - Richland, WA
              1991 Hawk GT
              1997 VFR

              Comment


                #8
                lots of these guys love the vacuum pump mod. Its not for me.... I bypass the relay and thats that. There are a multitude of electric fuel pumps that can work,


                That said WW maked a dope mount for the vacuum pump, and jd sells the pumps, and there is a lot of knowledge about the system on here as its a well walked path. So you cant go too wrong with it
                Don't spend money and buy, spend time and learn.

                Comment


                  #9
                  There is nothing "special" about that relay.
                  Run down to your local electronic supply and pick up a 6 or 10 amp 12v relay and wire it up to the Honda plug.
                  Simple, costs about $2

                  A Mikuni pump will work, but the pump doesn't pump till the motor starts.
                  The OEM Honda pump is also nothing special, and not terribly robust. I have a Holley pump that has been faultless for years and years and years. If you use an aftermarket pump be aware they come in different "sizes" or pressures. You WANT about 6 or 7 PSI, the needle valve will leak at 10 PSI.

                  Comment


                    #10
                    Lots of useful info, thanks.
                    I can't buy the stuff you guys recommend since I'm not in the USA, but I'll check for similar stuff here when my pump breaks

                    Comment


                      #11
                      Originally Posted by bitzz View Post
                      There is nothing "special" about that relay.
                      Run down to your local electronic supply and pick up a 6 or 10 amp 12v relay and wire it up to the Honda plug.
                      Simple, costs about $2

                      A Mikuni pump will work, but the pump doesn't pump till the motor starts.
                      The OEM Honda pump is also nothing special, and not terribly robust. I have a Holley pump that has been faultless for years and years and years. If you use an aftermarket pump be aware they come in different "sizes" or pressures. You WANT about 6 or 7 PSI, the needle valve will leak at 10 PSI.
                      oem pumps @ 3psi.
                      "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.

                      Comment


                        #12
                        When the fuel pump died on my CB-1, I replaced it with a Facet 40171 electronic pump. These are utilized in small engine aircraft, and if they can keep a plane aloft, they can certainly keep a Hawk on the road. Of course mounting said pump would take some effort, but they work like a charm on the CB-1’s, so may be applicable here.

                        I have utilize the Mikuni mechanical pump since I first built my bike. It’s been bulletproof, but keep in mind there will be some cranking involved to fill the bowls as it is a vacuum system, whereas the OEM pump is pretty much instantaneous with fuel flow…
                        This forum is entirely dedicated to wasting time and money modifying a slow motorcycle. - joel

                        Nothing like a project to keep you busy, slowly draining funds out of the wallet! - spacetiger

                        Our Hawks have all the power any mature, sensible rider can use on any street or highway without carrying around excessively unnecessary big-bore weight and power - squirrelman

                        Bike builds can be and most time are art and expression. To take something mass produced and impersonal and make something personal that you can't stop staring at as you walk away. There is nothing I find more satisfying than looking at something cool and beautiful and thinking "I made that". - 6

                        Comment


                          #13
                          Originally Posted by bitzz View Post
                          There is nothing "special" about that relay.
                          Run down to your local electronic supply and pick up a 6 or 10 amp 12v relay and wire it up to the Honda plug.
                          Simple, costs about $2

                          A Mikuni pump will work, but the pump doesn't pump till the motor starts.
                          The OEM Honda pump is also nothing special, and not terribly robust. I have a Holley pump that has been faultless for years and years and years. If you use an aftermarket pump be aware they come in different "sizes" or pressures. You WANT about 6 or 7 PSI, the needle valve will leak at 10 PSI.
                          FYI, The vacuum pumps will pull as long as you can crank the motor and it has enough compression to run. It doesn't have to actually be running.
                          88 Blue Hawk GT - Under construction but rideable (guest approved)
                          89 BlackHawk 2.0 - On the lift and being assembled
                          90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                          Comment


                            #14
                            Originally Posted by squirrelman View Post

                            oem pumps @ 3psi.
                            Hey Jerry do you (or does anyone) happen you know what the flow rate is on the stock pump? I'm just curious. I figure given the story that the fuel pump was really just included to empty the tank I doubt it has to be very much.
                            88 Blue Hawk GT - Under construction but rideable (guest approved)
                            89 BlackHawk 2.0 - On the lift and being assembled
                            90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                            Comment


                              #15
                              Originally Posted by rpcraft View Post

                              Hey Jerry do you (or does anyone) happen you know what the flow rate is on the stock pump? I'm just curious. I figure given the story that the fuel pump was really just included to empty the tank I doubt it has to be very much.
                              From the FSM:

                              Turn the ignition switch ON and let fuel flow into the beaker
                              for 5 seconds, then turn the ignition switch OFF.
                              Multiply the amount in the beaker by 12 to determine the fuel
                              pump flow capacity per minute.

                              FUEL PUMP FLOW CAPACITY:
                              600 cc (0.630 US qt 0.528 Imp qt)/minute at 10 V​
                              "I couldn't afford NOT to buy it!"

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