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'82 XJ1100 idling issues and low RPM trouble

Discussion in 'XJ Technical Chat' started by Spycrab McGoo, Jun 29, 2020 at 8:42 AM.

  1. Spycrab McGoo

    Spycrab McGoo New Member

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    Hey all,

    I bought an '82 XJ1100 Maxim, and have absolutely loved it, but the bike has been giving me a slew of issues...

    Brief history on the bike, I bought it off a guy for cheap. It was running and riding, albeit with quite a few problems. It ran super rich so smoke was blowing out the exhaust, and the bike wouldn't start or run if there was any choke at all on it. Plus it wouldn't start unless the engine was already HOT. So you'd be sitting there just cranking the starter in short bursts for like 5 minutes and then it would finally turn over, and you had to sit there and rev it at 2500 RPM for another minute or two to warm it up. But after that, there were virtually no problems with riding it around. Throttle was responsive, shifted smooth, idled perfectly fine, etc.

    I tried working on it myself a bit, but eventually passed it off to a buddy of mine who has more tools and know-how than I do. Here's a quick list of what all was done to it;
    Replaced coils
    Replaced spark plugs and spark plug caps
    Float needles
    Intake manifold gaskets
    Float bowl gaskets
    Mixture screw o-rings
    Cleaned and rebuilt carbs
    Timed the carbs

    I got the bike back yesterday, and upon starting it this morning, it started right up no problem. The problem NOW is the engine idling speed, and trying to ride the bike at low RPMs.
    When the bike is idling, it dances around between 900 and 1200 RPM. Usually sits at 900 or 1000 and then pops up to 1200 (where it should be) for less than a second. The needle just keeps jumping. Which in and of itself, I wasnt SUPER worried about. But the big problem is when I try to start moving the bike, I HAVE to rev to about 3000 RPM and keep it there, otherwise the bike will stall out in first gear. Which, when I release the clutch, does 1 of 2 things; either it goes flying like a bat out of hell because i have to crank the throttle so far, or it bogs down to about 1500 to 2000 RPM and will not go any higher no matter how hard I twist the throttle until finally it decides to start revving higher. Usually when it bogs down to that 1500 to 2000 RPM, its shaking pretty violently, and while I'm cruising at low RPMs, I can hear the exhaust quietly sputtering the whole time, almost like really quiet consistent backfires.

    It seems like the bike was almost running better before everything got fixed up and cleaned, although it was definitely not running as efficiently as it is now.

    The weather is so nice lately and I dont feel safe or confident enough in the bike to ride it on the street. Im at my wits end trying to figure out what the next step to take is, so any help from you guys would be really appreciated.

    Thanks!
     
  2. FJ111200

    FJ111200 Active Member

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    Sounds like it's a carb issue.
    Is the throttle cable seated correctly?
    Obviously the mixture screws have been taken out to put in new o rings. Have they been set at the correct amount of turns out? I think is 2½ turns out.
    Timed the carbs? I think you mean synched or synchronised.
    Replaced the coils? Why? Are the HT leads fitted to the correct plugs?
    Have you spoken to your friend about your "fixed" bike?
     
  3. Spycrab McGoo

    Spycrab McGoo New Member

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    Throttle cable is all good. Im not sure about the mixture screws, ill have to check on that. I did mean synchronized, my bad, i always mix the terms. The coils were replaced in an attempt to fix the previous issue i had with starting the bike, which it did certainly help. All the leads are correct. And he was telling me about the idling issues when I got the bike back from him and we both aren't sure what the cause is. He said he took the carbs apart twice trying to see what the deal was. Its possible it could be the mixture screws like you're saying... If it's not that, do you have any other ideas what it could be?
     
  4. mlew

    mlew Well-Known Member

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    I bet your friend did not replace the throttle shaft seal when he had the carbs. Old dry seals are a common issue causing an inconsistant idle speed. Vacuum leaks on the intake boots are next.
    Have the valves been adjusted yet?
     
  5. Spycrab McGoo

    Spycrab McGoo New Member

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    He said he sprayed carb cleaner and starting fluid around the carbs to see if it affected how the bike idled, as apparently thats a way to test the throttle shaft seal, but he said it didn't change. But its no guarantee.
    The intake boots are solid from what I can tell, no cracks, splits, or rips.
    As far as the mixture screws go, he said he tried everything from 1 to 4 turns, but he said it was idling best around 3 to 3.5 turns.
    The valves have not been adjusted, however the bike has low mileage and we can't imagine it would need it unless the guy who had it before me did a terrible job adjusting. Which, to be fair, there was gasket sealer all up in the carbs that he sprayed in there, so who knows?
    The only thing leading us away from thinking its the valves is that the engine runs perfectly fine in higher RPMs, and the bike was able to run no problem before he got the gasket sealer and other gunk out of the carbs.

    I guess my big fear is, did the previous owner ruin the carbs?
     
  6. Huntchuks

    Huntchuks Active Member

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    Do the vacuum leak tests yourself, don't take the word of anyone unless you see them do it and do it using a method that can work. How did he adjust the mixture screws, by sound? All four turned out equal? Maybe they shouldn't be but you would need to ColorTune to find out. Throttle shaft rings replaced? Not unless he broke the rack apart. You have much to check.
     

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