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1983 GS 750E revs cut out at higher speeds

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    #1

    1983 GS 750E revs cut out at higher speeds

    Hey there,
    I've recently purchasede a 83 750E. When I'm in the 5th gear and the rpm is 4200 hundred the the bike drops in power and then powers up again. I'm losing power any time I let off the gas and then try to throttle up. The carbs are apparently in good shape and I put in premium gas. I looked inside the tank and I can not see and signs of rst, plus I do not run it right down in fuel. I've changed the oil. Who knows. any suggestions will greatly appreciated

    cory
    Tags: None
    #2
    I wouldn't trust the carbs to be good. Pull them and look. Its not a big job and it is the only way you'll know for sure.

    Before you go to that,however, grab a can of Seafoam and run it through a tank or two. Don't put more than 1/4 a can per tank.

    If the bike has sat for any time there will likely be crud forming as the gas starts to congeal. Seafoam will break this up.

    If there is no change after 2 tanks pull the carbs for a physical cleaning.

    Hope this helps.

    Let us know how it goes.

    Cheers,
    Spyug.

    Comment

      #3
      bogging

      your bike sounds like its bogging does this only happen @ 4200 or above 4200 as well?

      Comment

        #4
        I would check the petcock and the vent lines on the carbs. Also see if the gas cap vent is venting. When the bike is bogging see if you get a rush of air when removing the gas cap.
        1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
        1985 GS1150ES stock with 85 Red E bodywork.

        Comment

          #5
          Seafoam for the carbs, second vote for that. I mix it a little stronger in my bike,I have the same one. I put 3/4can in two consecutive tanks, then save the other half for a mid season tune up. Your bike will smoke for at least another tank of fuel after you finish running the seafoam through. Check your aircleaner, mine was hard as rock and clogged with dirt. A new Uni is only $20. Then check your petcock, naw, just clean the thing out. And change your plugs, surprising how they make a difference.

          Let me check though, if you are cruising at 4200rpm in 5th, that should be around 90k or so, then close off the throttle and come back on with the power, it hesitates, dies, boggs, what exactly?

          Comment

            #6
            1983 gs 750 bogging and hesitation

            Hey thanks everybody.
            To answer a few questions, at around 90k to 110k if I let off the throttle it hesitates when I throttle up. Yes it bogs as well. It takes a long time to warm up with the choke on, and it did sit for a considerable amount of time before I purchased it. I'm going to try the seafoam and see what happens. I'll replace the plugs too. I've never heard of the gas cap vent and is it relatively simple to locate the petcock and vents?
            thanks

            cory

            Comment

              #7
              Originally posted by corybsv View Post
              Hey thanks everybody.
              To answer a few questions, at around 90k to 110k if I let off the throttle it hesitates when I throttle up. Yes it bogs as well. It takes a long time to warm up with the choke on, and it did sit for a considerable amount of time before I purchased it. I'm going to try the seafoam and see what happens. I'll replace the plugs too. I've never heard of the gas cap vent and is it relatively simple to locate the petcock and vents?
              thanks

              cory
              The gas cap is vented. You may not be able to tell by looking at it put it allows air to enter the tank as fuel drains out to the carbs. If the vents get plugged then the gas will not flow sufficently to run the engine. The next time it bogs on you pull off to the side of the road and open the tank. If you hear air rush in then the vents are plugged and must be cleaned. The petcock is the valve on the bottom of the tank on the left side that has a small handle you use to select "On", "Pri" or "Res". I would guess you might not have ever used it and don't know what its for. The owners manual will tell you all about it. If you don't have the owners manual then buy a repair manual for it. To test it you'll need a piece of 5/16" fuel line, a piece of 1/4" fuel or vacuum line and a gas can. Put the petcock in the "On" position with the bike off and remove the fuel line. Its the big one. Put on the piece 5/16" hose and hold the other end above the open gas can. Turn the petcock to "Res" and see if you get a full flow of fuel out of the line. If you don't you'll need to rebuild or replace the petcock or clean out the tank. If it flows ok turn the petcock to "Res" and the fuel will stop. Pull the small line off the petcock and put the 1/4" on. If you have a vacuum pump attach it to the other end and put some vacuum in the line. If you don't have a vacuum pump then suck on the line. If the fuel doesn't flow and/or you get a mouth full of gas service or replace the petcock. If theres a fuel filter anywhere in the line throw it away. LOL!

              Comment

                #8
                Originally posted by fgh View Post
                The gas cap is vented. You may not be able to tell by looking at it put it allows air to enter the tank as fuel drains out to the carbs. If the vents get plugged then the gas will not flow sufficently to run the engine. The next time it bogs on you pull off to the side of the road and open the tank. If you hear air rush in then the vents are plugged and must be cleaned. The petcock is the valve on the bottom of the tank on the left side that has a small handle you use to select "On", "Pri" or "Res". I would guess you might not have ever used it and don't know what its for. The owners manual will tell you all about it. If you don't have the owners manual then buy a repair manual for it. To test it you'll need a piece of 5/16" fuel line, a piece of 1/4" fuel or vacuum line and a gas can. Put the petcock in the "On" position with the bike off and remove the fuel line. Its the big one. Put on the piece 5/16" hose and hold the other end above the open gas can. Turn the petcock to "Res" and see if you get a full flow of fuel out of the line. If you don't you'll need to rebuild or replace the petcock or clean out the tank. If it flows ok turn the petcock to "Res" and the fuel will stop. Pull the small line off the petcock and put the 1/4" on. If you have a vacuum pump attach it to the other end and put some vacuum in the line. If you don't have a vacuum pump then suck on the line. If the fuel doesn't flow and/or you get a mouth full of gas service or replace the petcock. If theres a fuel filter anywhere in the line throw it away. LOL!
                The first Res he states should be prime.
                1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
                1985 GS1150ES stock with 85 Red E bodywork.

                Comment

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