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  • O.T. Motorcycle won't rev

    I have a 94 Honda Magna v750. New rider, pretty inexperienced. Anyways,
    old story. Quit riding it for a while ( about a yr ) .. ran ok when parked.
    But after a yr sitting it ran really bad.

    My buddy said he would look at it and its been sitting at his place
    for 2 yrs now.

    Well he just moved and I have it back and would like to get it going.

    symptom: it starts right up and idles nicely. But when you give it
    gas, it either does little or shuts off.

    Do you guys think I might get away with pulling the air cleaner and
    pouring some seafoam into the carbs, or am I going to end up
    rebuilding the things.

    That is of course if you guys agree it IS the carbs.
    John Titor, when are you.

  • #2
    Originally posted by Mike Amick View Post

    symptom: it starts right up and idles nicely. But when you give it
    gas, it either does little or shuts off.


    2 years... Gas has likely gone bad. Empty the tank. Replace the filters. Clean out the carb float bowls.

    If that does not work, the other thing to suspect is a clogged main jet.

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

    Comment


    • #3
      Sitting, The fuel delivery piping may very well have corroded and clogged. That is why the engine will idle, but not rev or deliver power. The fuel is just not there.

      Rebuild? only the carbs need attention. The engine is fine.

      Thank the EPA and the "Alcohol consortium" for your troubles.

      Comment


      • #4
        What Dan said. Wish I had better news.

        Unfortunately this is what happens when float bowls aren't drained before storage. Fuel degrades over a relatively short time and turns into a residue that can be very difficult to remove. Sometimes you can get lucky and dissolve them chemically but more often than not physical removal techniques are required.
        The carbs on your bike are constant velocity type units, they rely on light springs and and vacuum to operate a flexible rubber diaphragm which in turn lifts a tapered needle though the main jet. The fit of the needle piston in the carb body is very precise and may be sticking, rendering the higher speed circuit inoperative. The transition fuel circuit from idle to main needle jet is the pilot jet circuit, it may also be plugged.

        Removal of the carbs is a last resort as the bike is literally built around the carbs, not the easiest job even if you are comfortable doing this sort of stuff. If it were me I would first gain enough access to the carbs so that I could see down inside all 4. Check for free movement of the slides, they should move very freely. You may as well drain the float bowls as well although I suspect that if you have it idling well at this point you won't find much here.
        Fuel degradation and corrosion play havoc inside the carb's tiny air and fuel metering circuits so I would be very doubtful if mechanic in the can will be of any help but you have nothing to loose and everything to gain here so give it a shot and give it time to work.
        Last edited by Willy; 05-30-2015, 12:47 AM. Reason: spelling
        Home, down in the valley behind the Red Angus
        Bad Decisions Make Good Stories​

        Location: British Columbia

        Comment


        • #5
          Thanks .. gives me some things to look at.
          John Titor, when are you.

          Comment


          • #6
            I have seen dirtbikes and small engines bounce back with new premium fuel and extended cycles of idling with occasional gentle revving to try to open up plugged vacuum circuits... think of it as an extended solvent bath. Watch the temp and make sure the T-stat and fan are working properly and that it does not overheat. Before you do that make sure you do an oil change, oil has a shelf life, the additives break down and motorcycle oil is very dependant on those additives... esp. wet sump bikes like yours.

            Comment


            • #7
              Oil has a shelf life?

              Please , tell us more details.

              Comment


              • #8
                Definitely carb issue. From the tank to the bottom of the bowls, all needs to be cleaned.

                Comment


                • #9
                  You will have to remove the carbs take them.apart and clean them , a tip for.preventing this is a good 2 stroke mix HEAVY like 12 to 14 ounces to 1 one gallon of gas in the tank and ride it around for a bit before you store it works perfect ! It wont keep the gas from going bad after storage you will have to drain and put fresh gas in it but it keeps the gas from turning into jello ,

                  Comment


                  • #10
                    Not just the jets too, sometimes the small orifices in the carb body get blocked and need attention.
                    I always strip and rebuild the whole carb, paying attention to jets, passageways and also that the diaphragm isnt torn if they are CV carbs like I think yours are. I stretch them out lightly to highlight any tears in them during inspection.

                    Comment


                    • #11
                      try fresh fuel witn no methenol. I bought a Bombedier step thru 500 4wd with 100 miles a year & it did the same thing put in fresh fuel & slowly it got better & if fine but it's a thumper so only one carb & I got lucky. Good luck!

                      Comment


                      • #12
                        Originally posted by 19673ontree View Post
                        You will have to remove the carbs take them.apart and clean them , a tip for.preventing this is a good 2 stroke mix HEAVY like 12 to 14 ounces to 1 one gallon of gas in the tank and ride it around for a bit before you store it works perfect ! It wont keep the gas from going bad after storage you will have to drain and put fresh gas in it but it keeps the gas from turning into jello ,
                        This is what I do. Strong 2-stroke mix, run it to warm up, then shut off the fuel and let it run out at idle. Use the left over 2 stroke mix in the lawn mower or snow blower etc. My wood splitter and wood hauler has burned a lot of it.
                        Other option is to use real gasoline without alcohol in it, doesn't go bad as fast.

                        Comment


                        • #13
                          Originally posted by CalM View Post
                          Oil has a shelf life?

                          Please , tell us more details.
                          I think their talking about petrol, the light fractions evaporate leaving pump poo,
                          Mark

                          Comment


                          • #14
                            Rather you than me. What the other guys said apart from "small dirt bike engine" etc. Jeez V4 Magna, and 4 carbs, and not easy to get at, couple of hours before they are even off the engine. Best of luck. Why i like my twins, and carbs out in the open, i like Simples.

                            Comment


                            • #15
                              Best way to clean the carbs (off the bike) is to boil them in a solution of 4:1 distilled water:lime juice for an hour, followed by a rinse, followed by another boil for an hour with just distilled water. The castings will look like new and any hidden plastic parts won't be damaged. Do this outside (it stinks to high heaven) and maintain the liquid level (it will evaporate quickly. I've bought irreplaceable carbs back to life with this method.

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