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    Marvel Mystery Lug

    Sorry for the novel. In case there's something I missed, wanted to get it all out there.

    I got my bike last spring. It had been sitting outdoors for several years and needed some serious love:

    Rusty tank was cleaned and epoxied, carbs were professionally cleaned and tuned. That got it running although still not all that well with serious hesitation before it would really take off and truly awful running before it was 100% warmed up. The air box snorkel was missing so that was replaced and a few tanks with some fuel system cleaner (Seafoam?) seemed to get it running better although it still had no power when not fully warm and it had a tiny lug at high speed (65+ mph).

    This winter, I did the shims, replaced both the carb and air box boots and sealed the air box along with a new filter. The new filter may have gotten a little too much oil (I used motor oil) but I let it sit for a couple days, wrung out the excess that collected at the bottom and sopped up the pooled oil so it shouldn't have been too bad. Also cleaned and put new seals in the leaking timing chain tensioner.

    At that point, it ran 90% better. It maybe seemed to lose a little bit of power at WOT and still had that slight lug at highway speeds. I assumed it needed to have the carbs vacuum synched after messing with the valves and boots but haven't gotten that done yet.

    So here's the deal: A couple days ago I topped it off with fuel after the ride home and added a quarter cup of Marvel Mystery Oil to the fuel. My dad swears by the stuff and the internet doesn't seem to have anything bad to say about it so why not? After reading up on the lug here at GSR, I took the cover off the gas cap and blasted it out with some WD-40 although there was no visible gunk anyway. Apparently I had topped it off a little too high as the next day, there was a small pool under the bike. I cleaned it up and noticed it was a little oily and wasn't really evaporating like gasoline should, probably because of the MMO that was poured in on top of the gas. There didn't appear to be any on the bike so I assumed (and still do assume) that it drained cleanly out the overflow tube and caused no problems.

    Only there are problems. On the next ride, it ran absolutely flawlessly until it got up to highway speeds and then started with that same lug. Only this time, it quickly went from a slight lug to a bad lug and then got so bad it could barely maintain speed. At 55 and below, the lug goes away. At hard acceleration or higher cruising speeds, it comes back.

    It sounds like a fuel problem and the MMO makes me think some dirt or whatever got knocked loose by the solvent and plugged up a choke point, maybe at the petcock or fuel line but more likely a jet. The fuel line appears to be old so I ordered a new OEM one and will replace the newer-looking vacuum line as well just for the heck of it. I'll also pull the petcock and look it over. If that doesn't help, is it time to pull apart the carbs or is there some other thing that could be the issue?

    Again, sorry for the novel.

    #2
    Probably not the lugging issue but, with all the work done on the carbs and intake system, you NEED to do a vacuum sync or you're just wasting time.

    With that said, it's probably going to need a complete strip and dip of the carbs again. MMO is not going to solve your problems.

    Top end power loss is going to be either a restricted fuel system or a main jet issue if it even is fuel related. I'd do a plug chop at 3/4 to WOT and see what the plugs look like.
    http://img633.imageshack.us/img633/811/douMvs.jpg
    1980 GS1000GT (Daily rider with a 1983 1100G engine)
    1998 Honda ST1100 (Daily long distance rider)
    1982 GS850GLZ (Daily rider when the weather is crap)

    Darn, with so many daily riders it's hard to decide which one to jump on next.;)

    JTGS850GL aka Julius

    GS Resource Greetings

    Comment


      #3
      Roger that. I've got a vacuum tool coming in the mail along with a colortune so the carbs' settings can be taken out of the question once that's done.

      Originally posted by JTGS850GL View Post
      Probably not the lugging issue but, with all the work done on the carbs and intake system, you NEED to do a vacuum sync or you're just wasting time.

      With that said, it's probably going to need a complete strip and dip of the carbs again. MMO is not going to solve your problems.

      Top end power loss is going to be either a restricted fuel system or a main jet issue if it even is fuel related. I'd do a plug chop at 3/4 to WOT and see what the plugs look like.

      Comment


        #4
        I didnt see anything about valve adjustments, checking the timing, seeing if the petcock filter inside then tank is clogged, what the "professional" did to the carbs, for instance:

        NEW orings throughout?
        Float hts adjusted?
        Carbs dipped..or how ( or even if ) the bodies were serviced at all?
        Where are the fuel screws at the top rear set at?
        Did the PRO break off any fuel screws tips insdie the carb bodies and not know it?
        Have the intake manifold orings been replaced?
        Is there an inline fuel filter between the tank and carbs ( other than the petcock itself )?
        Are you 100% certain the petcock is functioning and flowing fuel properly?
        Any pin holes in the slide diaprams that didnt get found by the pro???

        See my point here???? theres a dozen things that MUST be checked and eliminated or else your chasing a ghost till he!! freezes over. And , as many here will attest to, the guys at " the shop" do the very very minimum to get it running. You need answers from the guy that did the carbs and then we can go forward.

        Look here on the right side under the manuals menu board and youll see the CV CARB REBUILD TURTORIAL. And robertbarr here on the forum has a business specialising in the oring kits and intake manifold orings for cheap.

        Manuals and carb tutorials here...



        oring kits here...

        MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
        1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

        NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


        I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

        Comment


          #5
          Points well taken. The valves were just checked and the intake orings were replaced along with the boots so that's not an issue. I will take a look at the timing and actually have a set of orings from cycleorings already so I'll take a crack at the carbs over the weekend. Reading through the carb cleaning guide, it looks like it will be almost as much fun as I imagined :\. Truly, I have no idea what Dave the bike guy did to the carbs other than that he said he disassembled and cleaned them. He's done good work on other bikes so there's no reason to doubt him but it's absolutely worth taking a look now that it isn't running right.

          Originally posted by chuck hahn View Post
          I didnt see anything about valve adjustments, checking the timing, seeing if the petcock filter inside then tank is clogged, what the "professional" did to the carbs, for instance:

          NEW orings throughout?
          Float hts adjusted?
          Carbs dipped..or how ( or even if ) the bodies were serviced at all?
          Where are the fuel screws at the top rear set at?
          Did the PRO break off any fuel screws tips insdie the carb bodies and not know it?
          Have the intake manifold orings been replaced?
          Is there an inline fuel filter between the tank and carbs ( other than the petcock itself )?
          Are you 100% certain the petcock is functioning and flowing fuel properly?
          Any pin holes in the slide diaprams that didnt get found by the pro???

          See my point here???? theres a dozen things that MUST be checked and eliminated or else your chasing a ghost till he!! freezes over. And , as many here will attest to, the guys at " the shop" do the very very minimum to get it running. You need answers from the guy that did the carbs and then we can go forward.

          Look here on the right side under the manuals menu board and youll see the CV CARB REBUILD TURTORIAL. And robertbarr here on the forum has a business specialising in the oring kits and intake manifold orings for cheap.

          Manuals and carb tutorials here...



          oring kits here...

          http://cycleorings.com/

          Comment


            #6
            Not trying to throw the guy under the bus.....wasnt the intent of my post. BUT there are folks here that once worked at shops and have actually admitted to the fact that its about "get it to run and get the cash with the least amount of time and work".

            And all the years I have worked on bike the other guy worked on first has beared that ugly little secret an absolute truth. I think many here will back me up on that!!! Basically the way I see it...and its just my opinion...if I havent done it myself and double checked I do not trust my bikes reliablity or my personal safety to anyone but myself.
            MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
            1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

            NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


            I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

            Comment


              #7
              The fuel line was cracked. Problem solved.

              Comment

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