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Petcocks or Carbs?

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  • #1

    Petcocks or Carbs?

    I was at an advanced motorcycle course yesterday. Bike was pulled out of storage the other week. Petcock rubber was stiff.

    This was my second time riding the bike. First 120 miles was un-eventful. Halfway through the course, the bike started sputtering like it was running out of fuel. I thought maybe it was getting too hot. Anywho, running the bike on "Prime" solved the issues. Reserve had same issues. So, either my vaccum lines are messed-up, or the petcocks are acting funny. Gonna run the tank dry and pull the petcocks and see if anything looks hinky.
    1979 XS1100F
    2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.
    Tags: None
  • #2
    May need to remove petcocks from tank and check the factory plastic tower screens for restrictions.
    81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

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    • #3
      let us know

      Hey Ian,,,same exact thing happened to my xs the other day,,,put on prime and it ran great. Sooo,,,,maybe save me a step or two and if you had anything wrong with the petcocks or screens in the tower. I pulled off the gas cap and clean the vent as it was dirty but havent taken it out to see if that was it. Anyway,,,,my xs did the exact thing as yours so If you could keep us updated to your results, thanks, Mike in SUn Diego
      mike
      1982 xj1100 maxim
      1981 venture bagger
      1999 Kawi Nomad 1500 greenie
      1959 wife

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      • #4
        Hey Mike-

        I'll certainly keep you updated. The petcocks were extremely stiff coming out of storage. I also added a quarter can of Seafoam to the first tank of gas (the other day was tank #2). Just weird that the bike started acting up mid-day. I have not counted ANYTHING out. I may not be able to get to it for a few days, as work, gf, and the other bikes are keeping me busy. Thanks for the replies.
        1979 XS1100F
        2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

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        • #5
          Make sure a vacuum line to the petcocks has not cracked or detached.
          "Time is the greatest teacher; unfortunately, it kills all of its students."

          Comment

          • #6
            If it works okay on prime the screens are probably okay. There's some funky stuff inside those vacuum operated petcocks - springs, weird rubber gasket, and diaphrams. I ditched the vacuum operated petcocks on my F model years ago and never looked back. Instead I use manual petcocks in conjunction with viton tipped fuel valves, and I just leave them on all the time. The viton provides a good seal and I don't get anything leaking past the valves, and they provide the same kind of function that the vacuum operated valves do - which is basically get on and ride. Course the other way to work 'em is to turn the petcocks on and off.

            Before I installed the manual petcocks I tried rebuilding the stockers. Never could get 'em to work right. I used the petcocks and mounting plates from Parts N More for about $40 ea., and they've worked great. My brother has the same petcocks on his G model, and they're doing the job there too. They require a tiny, tiny bit of grinding around the petcock opening to accommodate the round towers, but that's the only mod needed.

            JAT
            I think I have a loose screw behind the handlebars.

            '79 XS11 Standard, Jardine 4/1, Dyna DC1-1 Coils, 145 mains, 45 pilots, plastic floats - 25.7mm, XV920 fuel valves, inline fuel filters, speed bleeders, Mikes XS pods, spade-type fuse block, fork brace, progressive fork springs/shocks, manual petcocks, 750 FD, Venture cam chain tensioner, SS brake lines

            Comment

            • #7
              That's a mod I'll keep in-mind down the road. I re-built the petcocks last riding season.
              1979 XS1100F
              2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

              Comment

              • #8
                Left-side vacuum hose came loose. Back-on, runs like a champ!
                1979 XS1100F
                2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

                Comment

                • #9
                  Originally posted by IanDMacDonald View Post
                  I was at an advanced motorcycle course yesterday. Bike was pulled out of storage the other week. Petcock rubber was stiff.

                  This was my second time riding the bike. First 120 miles was un-eventful. Halfway through the course, the bike started sputtering like it was running out of fuel. I thought maybe it was getting too hot. Anywho, running the bike on "Prime" solved the issues. Reserve had same issues. So, either my vaccum lines are messed-up, or the petcocks are acting funny. Gonna run the tank dry and pull the petcocks and see if anything looks hinky.
                  Originally posted by LoHo View Post
                  Make sure a vacuum line to the petcocks has not cracked or detached.
                  Ha ha ha ha ha........haven't we been through this before Ian?
                  Greg

                  Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                  ― Albert Einstein

                  80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                  The list changes.

                  Comment

                  • #10
                    Yup, and I bought new lines and clamps, and one of them still fell-off. I'd rather it be that, than something else!
                    1979 XS1100F
                    2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.

                    Comment

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