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  • low rpm stumble

    OK, I am another new member to this site and have already used the expertize and wealth of information to get my bike running (sort of). Sorry for the long post but I want to give you all the info.

    The bike is an 1981 midnight special and was parked for 3 years before I purchased it. It has 46000 KMS (25000 miles). I have taken it to a mechanic and had the Carbs cleaned, new slides,needles and seats,carb holders,air cleaner,plugs. I have checked the pickup coil wires and the vacume advance module and all seem to be working. It has 110 main jets in all 4 which are original. I am also running a 4 into 1 header which seemed to improve the performance over the stock exhaust which was rusted and broken.The floats are set at 24 and I have had a carb sync done. Now my problem.

    The bike idles great and revs with no hesitation while in neutral, or in gear when it's cold. The problem arises when it has a chance to warm up a bit. It will still rev in neutral but as soon as I let out the clutch it stumbles until the RPM gets up to approx 3000 then takes off like an xs1100 should. Cruising in 4th at 35-40 mph it has a slight miss, want's to buck a bit, if i get the RPM up is runs great. When it's warm it also is hard to start after it has sat for 10 or 15 minutes. The only way it will start when its warm is if i roll on the throttle approx 1/2 way. I have checked the gas milage and right now it gets approx 25 MPG, not anywhere near the 35-40 mpg that it should be getting. I have checked the plugs and they seem to be the right color except #2 and 3 which seem ro be burning a little rich (slightly darker than the other 2). The bike starts fine even without the enricher when its cold.

    I am at a loss to what's causing this and after reading all the posts and the tech tips am unable to find anyone that has a similar problem. Any ideas what the problem may be? Any help will be appreciated.

    Darrell

  • #2
    Here is the CLUE:The bike starts fine even without the enricher when its cold !!
    Check wit hthe mechanic who did the carbs. Did he change the pilot jets? did he use AFTERMARKET jets?
    My guess is he didn't use the stock pilot jets, but went for K&L junk!!
    You are running way rich at low RPM, and you need to recheck the pilot jets.
    When properly jetted, these bike MUST use the "choke" to start cold. Your milage should be in the 35MPG range, US gallons.
    Ray Matteis
    KE6NHG
    XS1100 E '78 (winter project)
    XS1100 SF Bob Jones worked on it!

    Comment


    • #3
      Hey Darrell,

      I concur with DiverRay on that you probably got a set of the ill fated K&L pilot jets instead of stock MIKUNI!! Even with trying to adjust the pilot screws down, you'll still be way to rich until you change the pilot jets! Once you have the throttle cracked and get above 3-4K, then you're getting into the mains and getting enough air with the fuel to run more efficiently, but the pilots still contribute and so can still be causing it to be too rich even then!
      T.C.
      T. C. Gresham
      81SH "Godzilla" . . .1179cc super-rat.
      79SF "The Teacher" . . .basket case!
      History shows again and again,
      How nature points out the folly of men!

      Comment


      • #4
        35mpg? I guess there's something wrong with my bike then...I get about 44mpg. ; )

        I'm not complaining though, gas prices here in hawaii are about $3.70/gal last time I got gas. The bike's a hell of a nice alternative to my 10mpg '86 full size Bronco.
        __________________________
        Jon Groelz

        '82 XJ1100J-John
        '78 XS1100E-Name Forthcoming (It's a Girl!)

        Comment


        • #5
          44 mpg wow!

          That is great gas mileage, I get about 30, but am putting new needles and seat o-rings in and will have the carbs synched early next week
          (messed up and ordered by e-check instead of visa check-card, confused the numbers and used checking account instead )

          but I hope all this effort raises the mileage some, I did redo all my brakes, calipers and master cylinders and got them to stop sticking and dragging on the rotors and it helped raise me at least 5 mpg, so I'm crossing my fingers on raising it some more.

          BTW I have indy style air filters and 4-1 exhaust on my xj and the mains and pilots are still stock but I had good color on the plugs, and it ran great, not sure about over about 100 mph, cause I just have stock speedo, but was very satified with power and performance.
          '82 Xj1100j

          "Ride for the Son"

          < )) ><

          John

          Comment


          • #6
            I have finally got time to get into the carbs and I couldn't tell if the pilots were OEM or not. I tried to order 42.5 pilots and was unable to get them. I did pick up a set of 110 mains and can get a set of 40 pilots. My question is will the 40 pilots work or will it cause the bike to run too lean. If the 40's are too lean where can I get a set of 42.5's?

            Comment


            • #7
              I would try and locate the 42.5's (see Dennis Kirk catalog). The 42's are pretty small. You might have to unscrew the pilot screws too far to compensate.

              Originally posted by cokeman
              (snip)I did pick up a set of 110 mains and can get a set of 40 pilots. My question is will the 40 pilots work or will it cause the bike to run too lean. If the 40's are too lean where can I get a set of 42.5's?
              Skids (Sid Hansen)

              Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

              Comment


              • #8
                Try http://www.mikesxs.com/
                '82 Xj1100j

                "Ride for the Son"

                < )) ><

                John

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