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  • #16
    Hey Jim,

    I wasn't talking about SPEEDING around, but just shifting into a lower gear so the engine can run at a slightly higher rpm so the engine isn't lugged. At 25mph, I ride in 1st or 2nd gear!

    Loho,
    What 3rd jet?? There's the Pilot jet, and then the Main Jet, that's it! Yes, the mains are being used around 3.5k and above, the pilots still contribute but thru a diminishing affect as rpms and load increases. Depending on the riding situation determines the rpms you want to run in. 4k is fine for once you've reached cruising hwy speed on a flat road, but getting up to that speed is part of the fun, revving the engine to 6-7+Krpm in the first few gears to get you ONTO the hwy and up to traffic speed quickly, then shift up to the cruise gears. And when you want to pass, downshift a gear or two for a much faster passing event, than a slow ROLLON throttle acceleration. I want to get past a cage in minimal time!

    During my runs in the mountains at XS East, on many of the roads that had 35-55mph range of curves, I quite often just kept it in 3rd gear, and revved up and down as I went thru the curves, provided much more crisper throttle responses, and more effective engine braking at the higher rpms coming down!

    SO...it depends on what you're doing and what you want from the bike, that's why we have all of these wonderful gears go choose from!!
    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


    • #17
      Final update on this thread.
      After much banging of the head and frustration with this flat spot/hesitation around 2500-->2800 rpms, I decided to recheck the carb sync with the mercury stix. As soon as I got everything hooked up and started the engine to check the sync the thing purred all the way up to 3500 rpms with no hesitation at all.

      Humm, only difference was that I had the sync stix hooked up to the four vacuum ports instead of them being hooked up to the petcocks or sealed off with those little caps. I knew I didn't have a leak with the petcocks because I had just rebuilt them with new innards and all. That left the two little caps on #1 & #4. They looked ok but were a little "hard" (I guess 26 years of engine heat was too much for them) anyway, I replaced the two caps with short pieces of vacuum hose capped off with screws to seal the ends and - vola - engine runs like new. - no flat spot etc- I guess that even though I had those caps on with hose clamps they must have been leaking a little vacuum, just enough to create that flat spot.

      Just thought I would pass this on in case anyone else is still running with the original equipment caps on those ports.
      Missing Link
      Keep the Shinny Side UP!!

      Comment


      • #18
        Good find!

        Originally posted by missinglink
        Final update on this thread.
        Skids (Sid Hansen)

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

        Comment


        • #19
          TC, not trying to be smart here but if I'm not mistaken: pilot jet, needle jet, main jet and air jet. 4 jets??? pilot 0-1/4 throttle, needle 1/4-3/4 throttle, main 3/4-full throttle, air jet for tweaking mix as well?
          2010 Kawasaki Z1000
          1979 SF: Millennium Falcon, until this Saturday

          Comment


          • #20
            Hey Tom,

            Not trying to be dumb, but sometimes I still succeed!

            As I have stated before, I'm no true mechanical guru, just an enthusiast with lots of computer time! I've learned alot in the last few years being on the forum, and I'm learning more every day!! Since my last post in this thread....note date:June, I have since come to realize that the emulsion tube IS another jet, the needle jet to be exact! I just didn't think about it that way, just an atomizer that the Main jet screwed into, kinda like the pilot screw for the pilot jet.....in my feeble mind anyways!

            So....yes, Tom, there are 3 fuel jets, and the air jet, however the pilot and Main are the ones most folks change when making adjustments to their mixtures! Thanks for bringing to light an recent addition to my knowledge base!
            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
              I wish that I was a little LESS familiar with the BS34's. I've got a pretty good handle on the fuel jet operation, but the air jet still stumps me somewhat! The 2 sets of carbs I just picked up (BS34II) had 140 mains (perhaps 4-1 exhaust?) but 210 air jets instead of the 180. Weird. Once my bike is dialed in with my exhaust I think I'll buy a few different sized sets of the air jets to see what happens with them. Who knows? My wife is kind enough to empty the "brass screw/nut thingies" out of my play jeans before washing the carb cleaner out. I may own an XS, but I'm a lucky man, regardless.
              2010 Kawasaki Z1000
              1979 SF: Millennium Falcon, until this Saturday

              Comment


              • #22
                Hi Guys, I've been reading your responses to this situation but was wondering what RPM level is the best for shifting these great machines. I try to shift at 4k but is it better to drag it out to a higher RPM when shifting? It sure seems to run better with the RPM level higher. Just curious what the rest of you guys do whem it comes to shifting. Thanks, Cameron
                Cam

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                • #23
                  Personally, I wind it out a little more, to maybe 5 K. Like TC, I'm not much on "lugging" the engine on my XS. I suppose it's personal preference for the most part, and how well your XS runs!
                  2010 Kawasaki Z1000
                  1979 SF: Millennium Falcon, until this Saturday

                  Comment


                  • #24
                    Thanks for the reply. I find that it runs a little rough when accelerating up from 2.5k in a higher gear so I usually run it in the next lower gear. It runs a lot better. I have always wondered if revving it higher is hard on the engine but I think these machines are made for it, in fact, probably need to be run a little harder than I run mine. Thanks, Cameron
                    Cam

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                    • #25
                      Hey, lisk, better check those vacuum caps. That's exactly the problem I was having. Just a little roughness/stumbling when reving from 2.5k thru 3.0k. Above 3K it ran like a scalded dog (not that I ever saw one of those...)

                      After I replaced those caps the bike accelerates with no hesitation whatsoever.
                      Missing Link
                      Keep the Shinny Side UP!!

                      Comment


                      • #26
                        Hey Lisk,

                        Like Tom said, shift WHEREVER you want!! When I'm accelerating onto the highway I'll shift at 7K!!!! Moves really fast that way!!

                        I don't even run it below 3K, it likes 4-6k range alot! Plus you have better faster throttle response without the need to downshift! When putting around, I'll shift earlier at a lower rpm, but these engines do like to wind out!

                        Just hang on tight when you start twisting that grip and letting it run up there, you'll believe it's a whole different motorcycle!
                        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


                        • #27
                          I've read that we run basically three circuits through the carbs, kind of a low/medium/high, and the biggest gas use is at the high circuit, where all three circuits are contributing gas. At the Yosemite Rally some years ago, an XSive mentioned that he gets over 40MPG when he keeps his RPMs below 4K. IIRC, 4K in fifth gear is around 55-60MPH, so it is slower than I like to go, plus when I'm riding with my neighbor who favors twisted up-and-down mountain goat trails, I like the revs higer to limit run-off speed and increase compression braking. I get only about 32MPG, so more miles on long trips is what I was seeking.

                          I also wonder: Is MPG a bell curve, so that at some low speed, MPG decreases due to inefficiency? I know that MPG decreases with speed, so what is the prime RPM range for good mileage?
                          "Time is the greatest teacher; unfortunately, it kills all of its students."

                          Comment


                          • #28
                            I get 40 mpg freeway driving only, 4800/5000 rpm (5000 rpm,70 mph) Around town varies because of how I ride it, from low to mid 30's. (YMMV) Stock exhaust/air box.


                            mro
                            80G

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