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  • General Performance Questions

    So, I've managed to get 3 tanks of gas through my bike since I've gotten it back on the road. I've noticed a few things and I was wondering if it's normal, or if my bike still needs a little tweaking.

    1) I'm getting just over 27mpg. This seems a bit low for the bike from what I've read on the forum, but then again, I do like to take off quickly, so maybe it's about right. Does 27mpg seem low to you guys?

    2) At idle, it's not possible to slip the clutch and have the bike slowly take off, I always have to crack the throttle as I'm letting out the clutch, generally I'll have to get up to at least 1500rpm before letting out the clutch or I'll stall. Is this normal, or should it have more torque at low rpm?

    3) power picks up pretty good at 2K rpm, and it's like a rocket from 3K up. I'm not even sure I've ever been able to use WOT, maybe perhaps for a few seconds on the freeway, but I don't remember hitting the stops before I had to slow down for traffic. Again, is this "normal" performance, or does it sound like I have a problem at the low end?

    I've got a 750 final drive ordered. I'm hoping to improve the mpg, but I'm a little concerned with the low end performance. Not too worried, I can always swap back to the original drive.

    New 4 - 2 exhaust on order too, without the crossover, does it impact low end, or top end?
    Guy

    1980 XS1100G - Frankenstein - resurrected from the impound lot
    1991 Suzuki GS500E (not running yet)
    2003 Burgman AN400 - Blue Belle
    2005 Burgman AN400 - Silver Belle

  • #2
    27mpg is pretty good if you do a lot of city stop and go riding.

    What have you got your idle set at?

    A standard w/17" wheel is the same gearing as a special w/a 16" wheel and the 850 FD. It'll be pretty tall geared with the 850 FD and the 17" tire.

    The Mac 4 into 2 takes a little away from the top end but not really that much. The power usually kicks in around 3K on up to about 7K on these engines so it soundsabout right .
    Greg

    Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

    ― Albert Einstein

    80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

    The list changes.

    Comment


    • #3
      Idle is set around 800. When warm, a little scratchy at idle, no hint of wanting to die though.

      It's kind of finicky first thing cold, spitting and popping, but by the end of the street it's warm enough to turn the choke off.

      Your comment about the 17" rear wheel and the 850 FD makes me glad I stuck with the 750 FD
      Last edited by Petersg_99; 02-20-2013, 10:42 AM.
      Guy

      1980 XS1100G - Frankenstein - resurrected from the impound lot
      1991 Suzuki GS500E (not running yet)
      2003 Burgman AN400 - Blue Belle
      2005 Burgman AN400 - Silver Belle

      Comment


      • #4
        I would consider 27 mpg low, but it really depends on your particular setup. Pods and/or aftermarket exhaust can kill mileage, as can riding habits. Upshifting too soon doesn't allow the motor to get to it's 'happy spot'.

        Your idle speed is too low; it should be around 1K rpm. Having to bump the throttle to take off is normal.

        And the 750/850 FDs are the same ratio. If you do mostly town riding, you will take a hit on low-speed performance and likely won't see a mileage increase.
        Fast, Cheap, Reliable... Pick any two

        '78E original owner - resto project
        '78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
        '82 XJ rebuild project
        '80SG restified, red SOLD
        '79F parts...
        '81H more parts...

        Other current bikes:
        '93 XL1200 Anniversary Sportster 85RWHP
        '86 XL883/1200 Chopper
        '82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
        Cage: '13 Mustang GT/CS with a few 'custom' touches
        Yep, can't leave nuthin' alone...

        Comment


        • #5
          Ok, I'll try bumping the idle up a bit, it's kind of embarrassing to kill the bike at a light

          On the ride to work, I usually get a good stretch of 4 or 5 miles at 45mph and with luck (and keeping the speed down) I don't hit the lights.
          Guy

          1980 XS1100G - Frankenstein - resurrected from the impound lot
          1991 Suzuki GS500E (not running yet)
          2003 Burgman AN400 - Blue Belle
          2005 Burgman AN400 - Silver Belle

          Comment


          • #6
            From my experiences, the performance your seeing is pretty normal as far as power band at 3k, and if you go above 5k and hit WOT, hang on tight!

            27 MPG avg is kind of low, I would recheck your tuning. also could just be due to you riding mostly in stop-n-go type traffic, or having a very quick right wrist.
            Life is what happens while your planning everything else!

            When your work speaks for itself, don't interrupt.

            81 XS1100 Special - Humpty Dumpty
            80 XS1100 Special - Project Resurrection


            Previously owned
            93 GSX600F
            80 XS1100 Special - Ruby
            81 XS1100 Special
            81 CB750 C
            80 CB750 C
            78 XS750

            Comment


            • #7
              I've always been told that idle should be at 1100. I agree though that there is not usually enough torque to make it move at that speed, unless it's already moving.

              Be sure your brakes are not sticking at all. A slight drag can decrease the MPGs significantly, as well as cause other problems.
              1980 XS850SG - Sold
              1981 XS1100LH Midnight Special (Sold) - purchased 9/29/08
              Fully Vetterized and Dynojet Kit added, Heated Grips, Truck-Lite LED headlight, Accel Coils, Irridium plugs, TKAT Fork Brace, XS850LH Final Drive & Black SS Brake lines from Chacal.
              Here's my web page devoted to my bike! XS/XJ User's Manuals there, and the XJ1100 Service Manual and both XS1100 Service manuals (free download!).

              Whether you think you can, or you think you cannot - You're right.
              -H. Ford

              Comment


              • #8
                Originally posted by CatatonicBug View Post
                I've always been told that idle should be at 1100..
                The '78-79 carbs are specced out at 950-1050 rpm, the later carbs 1100, probably because the later bikes run leaner. Anywhere between 1000 and 1100 should be fine...
                Fast, Cheap, Reliable... Pick any two

                '78E original owner - resto project
                '78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
                '82 XJ rebuild project
                '80SG restified, red SOLD
                '79F parts...
                '81H more parts...

                Other current bikes:
                '93 XL1200 Anniversary Sportster 85RWHP
                '86 XL883/1200 Chopper
                '82 XL1000 w/1450cc Buell, Baker 6-speed, in-progress project
                Cage: '13 Mustang GT/CS with a few 'custom' touches
                Yep, can't leave nuthin' alone...

                Comment


                • #9
                  Hard to say not knowing what's been done as far as carb work or ignition wiring testing. Lot of variables, but a not totally cleaned idle circuit, low voltage at idle can cause your low rpm starting out issue. If all is correct, with clutch engagement at idle rpm, the bike should not have any 'hiccups' and just smoothly accellerate with any applied throttle. Idle mixture may be a bit on the rich side also. Sounds like you got it pretty close, just not quite there yet.
                  81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

                  Comment


                  • #10
                    Originally posted by Petersg_99 View Post
                    So, I've managed to get 3 tanks of gas through my bike since I've gotten it back on the road. I've noticed a few things and I was wondering if it's normal, or if my bike still needs a little tweaking.

                    1) I'm getting just over 27mpg. This seems a bit low for the bike from what I've read on the forum, but then again, I do like to take off quickly, so maybe it's about right. Does 27mpg seem low to you guys?

                    2) At idle, it's not possible to slip the clutch and have the bike slowly take off, I always have to crack the throttle as I'm letting out the clutch, generally I'll have to get up to at least 1500rpm before letting out the clutch or I'll stall. Is this normal, or should it have more torque at low rpm?

                    3) power picks up pretty good at 2K rpm, and it's like a rocket from 3K up. I'm not even sure I've ever been able to use WOT, maybe perhaps for a few seconds on the freeway, but I don't remember hitting the stops before I had to slow down for traffic. Again, is this "normal" performance, or does it sound like I have a problem at the low end?

                    I've got a 750 final drive ordered. I'm hoping to improve the mpg, but I'm a little concerned with the low end performance. Not too worried, I can always swap back to the original drive.

                    New 4 - 2 exhaust on order too, without the crossover, does it impact low end, or top end?
                    Re "take off" difficulty ~~ these machines are really geared too high in first gear ~~ sorta like taking off in 2nd gear on other motorcycle types ; and even worse with 17" wheel. Some time back , I changed from 16" wheel to the 17" wheel ~~ mistake ~~ am now preparing the 16" wheel with new tire, and will reinstall.
                    JCarltonRiggs

                    81XS1100SH; WorkingMotorcycle,Not For Show,DeletedFairing,SportsterHL,
                    7½ gal. Kaw Concours gastank,1972 Wixom Bros. bags

                    79XS1100F; ?Parts?, or to Restore?

                    Comment


                    • #11
                      Another question crossed my mind. Since the bike uses a wet clutch we really can't play with oil additives like Lucas because we'll end messing up the ability of the clutch to engage properly correct?
                      Guy

                      1980 XS1100G - Frankenstein - resurrected from the impound lot
                      1991 Suzuki GS500E (not running yet)
                      2003 Burgman AN400 - Blue Belle
                      2005 Burgman AN400 - Silver Belle

                      Comment


                      • #12
                        Originally posted by Petersg_99 View Post
                        Another question crossed my mind. Since the bike uses a wet clutch we really can't play with oil additives like Lucas because we'll end messing up the ability of the clutch to engage properly correct?
                        Correct. Additives generally make the clutch slip.
                        Greg

                        Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                        ― Albert Einstein

                        80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                        The list changes.

                        Comment


                        • #13
                          Originally posted by Petersg_99 View Post
                          Another question crossed my mind. Since the bike uses a wet clutch we really can't play with oil additives like Lucas because we'll end messing up the ability of the clutch to engage properly correct?
                          Very likely..........and there's no magic in a bottle, but you initially might put several ounces of SeaFoam in a full tank of fuel and ride it a bit. If there's no improvement, might wanna go back thru carbs with a good cleaning and check some primary ignition voltages. Internally broken pick-up coil wire can cause similar issues, specially if the white wire is array internally.
                          81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

                          Comment


                          • #14
                            Hey there,

                            Along with NOT putting additives into the oil that have any friction modifying properties....if you have not replaced your OEM clutch springs, you could be experiencing a little slippage that isn't totally noticeable but could be robbing you of MPG? I didn't bother looking up your previous posts/threads to see the history of what you've done to the bike or what equipment it has on it now...ie. OEM exhaust, intake. Clogged or dirty air filter could cause loss. Underinflated tires....see the many threads recently on tires and recommended pressures and such.

                            As you being an Electrical Engineer I'm sure you've checked out all of your ignition components and brought them up to spec!

                            As has been stated, these engines are not harleys, they have power and torque, but you do need to give it a little throttle to get rolling. Also, as you've found, it likes to run near or above 3k rpm, but if you're running at 45 mph in 5th at 2k rpm, IMHO you're lugging the engine and that could also cause more fuel consumption having to input much more throttle in that gear/speed to get a modest increase in speed due to the increased stress with less leverage of the higher gear. Yes I have been informed that several members CAN roll on from 2k just fine, but there's a reason why we have 5 gears! I would suggest running the rpm a bit higher before shifting and then try to maintain a 3+ rpm level when cruising.

                            Aftermarket pipes have been reported to cause a slight loss of low end grunt, but folks usually couple these pipes with Pods, and in a recent thread discussion, "we" have come to the conclusion that the carbs like some form of velocity stack type intake flow, so mounting PODS on the ends of some tubes can helpe smooth the air flow out. And that has been reported to help with the low rpm throttle response. YMMV!

                            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


                            • #15
                              Deductions

                              I was gonna say the mileage was low, but you are using smaller gallons.
                              However I think I am doing better. It is probably your blasting off from the lights.
                              The amount of throttle for take off sounds about right, my Yami needs a few revs to get moving.
                              Yami also comes to life at around 3K revs, quite noticeable.
                              As for full throttle, I do that now and then but usually do not need it.
                              My much newer Suzuki has 124 HP for a 417 pound bike. Full throttle on that one gets your attention. It is a V twin so has a lot of bottom end grunt and runs to 11K.
                              Yami has the smoother engine.
                              Unkle Crusty

                              Comment

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