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  • #16
    81 Jet Sizes

    I bought my Special new and it came from the factory with 110 main jets on all four carbs. According to the shop manual the Standards had 120's for the center two cylinders and the outboards had 115's. I have a new set of Standard carbs in my stash and they also have this staggered jetting arrangement but they have rubber caps over the pilots and the 81 Special does not have these caps and so it appears the pilots in the 80-81 Standards are feeding off the mains like the 78-79 did hence the larger main jets. A stock 80-81 Special with a Kerker 4 into1 header which employ's Kerkers standard 1.5 inch glass wrapped baffle responds well with 112.5 mains,stock pilots and the idle screws tured out 3.5 turns from lightly seated.The 2 inch and 2.5 inch core will need 115's and in some cases the needles which are not adjustable with E-clips like the 78-79 will need to be raised with small .020 inch (1/2mm) thick washers. I used Kerker as an example but a similiar flowing pipe would get the same.The mains in a box stock 80-81 Special and Standard are close if your exhaust are stock but they are lean at idle and off idle and in the mid range as the factory leaned this part of the fuel curve down for cleaner emissions.The jet numbers I have mentioned are applicable for an altitude of sea level up to about 1500 feet. Generally,you decrease the main jet by 1# for each 2,000 feet of elevation increase.I live in St. Louis which has an elevation of about 450 feet but if I was in the mile high city of Denver my tune up would be dramatically different.The factory gave these things a tune up (jetting and so forth) that would enable them to be operated everywhere but because of the wide variance of altitudes in which they are used, they do not run perfect anywhere unless you tune them for your area.If you are not positive as to the application of the carbs you have,you can remove them and there will be a part number for the carbs acid etched somewhere on the main body of the carb.The numbers can sometimes be diffulcult to locate (I used a Magnifying glass to find mine) but the numbers are on there. Happy tuning.
    81 Black "1179" Xcessively trick Super Special. One owner (me).

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    • #17
      Well I've searched high and low lots of times tryin' to spot any sort of numbers or letters on XS11 carbs but never did see any, I always thought it was strange why no I.D. of what model carbs??

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      • #18
        Hey Dan,

        You may want to take a closer look at those Standard Carbs, since you said they have the pilot jet caps! Some folks have reported that they have found some bastardized type 80 series carbs that should have had the smaller mains and open pilot towers, but had the larger mains with capped pilot towers BECAUSE they had the sharing tunnel between the pilot and main jet towers! And the main jet needle/nozzle also had the hole in the side/end of it to allow the fuel to flow from the main jet tower thru that hole and sharing tunnel into the pilot jet! IF there is No tunnel, then the carbs used the smaller mains and NO caps on the pilot towers!

        Hey Orion, my 81SH also had the straight 110's from the factory, the book isn't always right!
        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!

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        • #19
          80 Standard carbs

          Originally posted by TopCatGr58
          Hey Dan,

          You may want to take a closer look at those Standard Carbs, since you said they have the pilot jet caps! Some folks have reported that they have found some bastardized type 80 series carbs that should have had the smaller mains and open pilot towers, but had the larger mains with capped pilot towers BECAUSE they had the sharing tunnel between the pilot and main jet towers! And the main jet needle/nozzle also had the hole in the side/end of it to allow the fuel to flow from the main jet tower thru that hole and sharing tunnel into the pilot jet! IF there is No tunnel, then the carbs used the smaller mains and NO caps on the pilot towers!

          Hey Orion, my 81SH also had the straight 110's from the factory, the book isn't always right!
          T.C.
          I bought these spare carbs new in 95 and they were the only set in the country that Donelson Cycles could find at that time.I have checked them for numbers and took the vacum diaphragms out for inspection and removed the float bowls and checked the main jets along with the pilot jet.The pilot was a 42.5 and had a rubber cap but was configured the same as the Pilots in my Special.The mains were 115 for 1&4 and 120 for 2&3.The needles were also different(thicker) than my Special but I cannot recall the part number but I have it in my notes.According to my book the main nozzles are 3H5-14941-02 which is also the one listed for an 81 Special.I have the original pilots from my Special but have replaced the pilots several times and I always order the jets from Donelson and over the years all the pilot jets I have ordered have all been of the same configeration except for the jet size.Elevens sold in California beginning in 79 had different pilot air jets,idle screw settings and main nozzles than the 49 state models.Dyno Jet kit's are sold for 80-82 Elevens in a one configeration for all and that's why the Dyno Jet kit doesn't work all that well,but as they say,if it doesn't work call Dyno Jet.Basically,I hope I never have to replace my original carbs with the spare 80 Standards as I would have to begin my tune up again from scratch and I am older and don't have another 25 years to trick out the Standard carbs.I am only kidding naturally,as switching them out would be no big deal.
          81 Black "1179" Xcessively trick Super Special. One owner (me).

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          • #20
            Well Dan,

            IF they don't have the tunnel between the main and pilot jet towers, then I would UNCAP the pilot towers IF you ever go to use those carbs or you won't have a pilot circuit! Sounds like someone may have put a carb kit in there, and found they had the rubber caps and the pilot towers were open and probably figured they went there, when they are only used for the 78-79 or 80's with that tunnel! The caps are otherwise thrown away for the 80-81-82 carbs that don't have that tunnel!
            But I'm sure you knew that! 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


            • #21
              Capped Off

              Originally posted by TopCatGr58
              Well Dan,

              IF they don't have the tunnel between the main and pilot jet towers, then I would UNCAP the pilot towers IF you ever go to use those carbs or you won't have a pilot circuit! Sounds like someone may have put a carb kit in there, and found they had the rubber caps and the pilot towers were open and probably figured they went there, when they are only used for the 78-79 or 80's with that tunnel! The caps are otherwise thrown away for the 80-81-82 carbs that don't have that tunnel!
              But I'm sure you knew that! T.C.
              These carburetors are new (never used) and have not been monkeyed with.I am familiar with the pilot jet circuits on the various carburetors used on the XS through the years it was produced.With the pilot jet plugged (shut off) or even partially plugged the motor will not run at off idle without the choke being pulled out or without racing the crap out of the motor, so if some idiot tried to run an Eleven with no pilot jet it would't take but a minute to realize he had a major malfunction.I have three junk XS carburetors that I have cut apart so I could study the fuel and air circuits and what better way to spend a cold winter evening in St. Louis than studying carburetor circuits........I know what your thinking..........Dan get a life!
              81 Black "1179" Xcessively trick Super Special. One owner (me).

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