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No vac to the vacuum advance?

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  • #1

    No vac to the vacuum advance?

    This is one of my famous "let's fix it until it's broke" events.

    I found one of those ratcheting cam chain tensioners and was dying to put it on. I'd been riding daily with no problems.

    I changed the tensioner without event, and change the oil while I'm at it. Rode out to school, noticing a little more cam chain noise than usual. Oh well, maybe it was too loose before.

    Riding home, the bike has no get up at all, which I recognize as vac advance problems. I try to fix it on the road, and can advance it by sucking on the vac hose...wtf?

    I get home and put a vac guage on the carb nipple and get intermittent vacuum, then none. How could a smooth running bike not have vacuum at the carb nipple? I put the old tensioner back on and adjusted it. The ratcheting tensioner had not extended, hence the cam noise. But the bike idles and runs well, except for the advance. If I'd done cam chain damage, the bike would be 86ed. Any ideas?
    "Time is the greatest teacher; unfortunately, it kills all of its students."
    Tags: None
  • #2
    By the way, anyone want a ratcheting cam chain tensioner cheap?
    "Time is the greatest teacher; unfortunately, it kills all of its students."

    Comment

    • #3
      hey Loho,
      Thats normal that there is no vacuum at the carb nipple at idle,

      with the hose attached to the vac advance suck on the hose and
      see if the vac advance holds vacuum, if it does then its working fine.
      pete


      new owner of
      08 gen2 hayabusa


      former owner
      1981 xs1100 RH (aus) (5N5)
      zrx carbs
      18mm float height
      145 main jets
      38 pilots
      slide needle shimmed .5mm washer
      fitted with v/stax and uni pod filters

      [url]http://www.youtube.com/watch?v=3pA8dwxmAVA&feature=mfu_in_order&list=UL[/url]

      Comment

      • #4
        Thanks Pete, but I know that the vacuum comes with revs. I'm saying there's no vac when reving the engine. I can suck on the hose when reving and get a smooth acceleration. I can't understand how vacuum could be lost, unless there's a vac leak somewhere else on the carb. And I can't think of something I've done to mess with that aspect.
        "Time is the greatest teacher; unfortunately, it kills all of its students."

        Comment

        • #5
          The only thing I can think of would be if a bit of 'stuff' (maybe the vacuum hose is going bad?) got sucked into the nipple at the carb. The orifice into the carb is much smaller than the nipple, so it wouldn't take a very big piece...

          If you have a vacuum pump, I'd try hooking that to the nipple and see if anything comes out.

          '78E original owner
          Fast, Cheap, Reliable... Pick any two

          '78E original owner - resto project
          '78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
          '82 XJ rebuild project
          '80SG restified, red SOLD
          '79F parts...
          '81H more parts...

          Other current bikes:
          '93 XL1200 Anniversary Sportster 85RWHP
          '86 XL883/1200 Chopper
          '82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
          Cage: '13 Mustang GT/CS with a few 'custom' touches
          Yep, can't leave nuthin' alone...

          Comment

          • #6
            Is it back to normal with the old chain tensioner on? If not then with the ratcheting chain tensioner you tried not being tightened, it's possible you jumped time a notch. Jumping one notch doesn't necessarily mean your valve train would be destroyed especially if you didn't rev it to high. It would have virtually the same effect as the timing advance not working. If it were me, I wouldn't run it again until you check the cam timing.
            "The Hooligan" XJ1100, Virago Gauge Pods, Screaming Eagle Mufflers, K&N Filter, hand made rear fender, side covers, and solo seat, round bar conversion, small headlight, tail light, and cat eye turn signals, chip fuses, rewired the right way.

            Pics: http://s1236.photobucket.com/user/ya...?sort=6&page=1

            Comment

            • #7
              i just went outside and connected a vac guage
              to the no 2 carb nipple, theres very little movement in the guage even
              when accelerating, max vacuum is obtained under hard decelleration.
              you could connect your guage up and ride the bike and see what
              readings you get.
              pete


              new owner of
              08 gen2 hayabusa


              former owner
              1981 xs1100 RH (aus) (5N5)
              zrx carbs
              18mm float height
              145 main jets
              38 pilots
              slide needle shimmed .5mm washer
              fitted with v/stax and uni pod filters

              [url]http://www.youtube.com/watch?v=3pA8dwxmAVA&feature=mfu_in_order&list=UL[/url]

              Comment

              • #8
                I wonder if the engine spinning and the vacuum are needed to open the vacuum advance. Hmm... Any thoughts?
                "The Hooligan" XJ1100, Virago Gauge Pods, Screaming Eagle Mufflers, K&N Filter, hand made rear fender, side covers, and solo seat, round bar conversion, small headlight, tail light, and cat eye turn signals, chip fuses, rewired the right way.

                Pics: http://s1236.photobucket.com/user/ya...?sort=6&page=1

                Comment

                • #9
                  If this all started after you changed the tensioner I would suspect you slipped a tooth on the cam chain at the crank. It happened to me and a few others. Removing the tensioner is a RED ALERT operation in my book now.

                  I'd make sure that didn't happen before doing anything else. Do a search on what to look for. Several threads on the subject.
                  79SF
                  XJ11
                  78E

                  Comment

                  • #10
                    Originally posted by SFerinTEXAS View Post
                    If this all started after you changed the tensioner I would suspect you slipped a tooth on the cam chain at the crank. It happened to me and a few others. Removing the tensioner is a RED ALERT operation in my book now.

                    I'd make sure that didn't happen before doing anything else. Do a search on what to look for. Several threads on the subject.
                    +1 on checking the valve timing. If it didn't damage any valves, check and if off VERY CAREFULLY reset the valve timing. The properly install the ratcheting adjuster, or if you don't want it now, I might be convinced to take it off your hands.

                    PS: hey! who changed the smileys around?
                    Cy

                    1980 XS1100G (Brutus) w/81H Engine
                    Duplicolor Mirage Paint Job (Purple/Green)
                    Vetter Windjammer IV
                    Vetter hard bags & Trunk
                    OEM Luggage Rack
                    Jardine Spaghetti 4-2 exhaust system
                    Spade Fuse Box
                    Turn Signal Auto Cancel Mod
                    750 FD Mod
                    TC Spin on Oil Filter Adapter (temp removed)
                    XJ1100 Front Footpegs
                    XJ1100 Shocks

                    I was always taught to respect my elders, but it keeps getting harder to find one.

                    Comment

                    • #11
                      Yeah, well, I guess now I get to check the timing. I'm guessing that if I slipped a tooth on the intake, the vacuum might be affected. But it starts and idles...oh well, I guess I'd better take a look. Another chapter in my book, "Failure Brings Knowledge: A Guide To Motorcycle Repair".
                      Last edited by LoHo; 03-09-2010, 02:52 PM. Reason: syntax error
                      "Time is the greatest teacher; unfortunately, it kills all of its students."

                      Comment

                      • #12
                        I'm still stunned that the ratcheting tensioner did not work. I took the end bolt/washer off, pulled the spring, and then the housing, and the tensioner arm was still retracted. I played around with it a lot before I installed it, and it never failed to extend full length and it looked like it was designed so that getting hung up was impossible. "I swear, this has never happened to me before, honey...."
                        "Time is the greatest teacher; unfortunately, it kills all of its students."

                        Comment

                        • #13
                          Bolt it back up and use an allen wrench or a phillips screw driver to push the plunger in before you put the spring and plug in. If it doesn't go, then you have something amiss in the intsall or inside the engine.

                          But, get the timing squared away first.
                          Ich habe dich nicht gefragt.

                          Comment

                          • #14
                            Did you put the vacuum gage on any of the other carbs?
                            They should show whats going on.
                            At idle they should all be the same vacuum. Are the carbs in sync?

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