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Pulsing front brakes on Special?

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  • #1

    Pulsing front brakes on Special?

    I keep reading about the front brakes 'pulsing' on the specials if the caliper mounting bolt is slightly bent.
    Any more info on this?
    I'm not sure if my bolt(s) are bent, (I don't remember anything out off the ordinary when I reassemble them last year) but when at a near stop (<10mph) my front brakes grab intermitently (ie pulse) and of course the bike tries to dive a little as the pads grab more then as the pads release, the bike comes back up.
    It's a little annoying, but the brakes DO grab well at speed and I don't feel any pulsing while zipping along. (example, on the interstate when traffic is suddenly stopped in front of me and I lay into the brakes and she slows down just fine, then when I get to about 5mph or so, it starts pulsing and doing the nose bob up/down. I just ease up on the front and finish slowing down with the rear.

    Any ideas of similar symtoms with anybody else?
    Hi, my name is George & I'm a twisty addict!

    80G (Green paint(PO idea))
    The Green Monster
    K&N A/F, TC's fuse block, '81 oil cooler, TC's homemade 4-2 w/Mac Mufflers, Raptor 660 ACCT
    Got him in '04.
    bald tire & borrowing parts

    80SG (Black w/red emblems & calipers)
    Scarlet
    K&N A/F, TC's fuse block, WJ5, Shoei bags, Raptor 660 ACCT.
    Got her in '11
    Ready for the twisties!

    81H (previously CPMaynard's)
    Hugo
    Full Venturer, Indigo Blue with B/W painted tank.
    Cold weather ride
    Tags: None
  • #2
    George,

    The first thing to try is cleaning the rotors. Get some 100 grit garnet paper and go after them. Sand them as well as you can followed by some brake cleaner. This might fix it.

    I recently went after a junkyard rotor with a paint stripping wheel. It cleaned it off real well. As it turns out, the rotor is warped. I can see it, as the caliper on my XS650 is moving in and out. I can not feel this when I apply the brake at any speed. Try the garnet paper.
    Marty (in Mississippi)
    XS1100SG
    XS650SK
    XS650SH
    XS650G
    XS6502F
    XS650E

    Comment

    • #3
      Thanks Marty, it may just be something as simple as that. I 'sticky' spot on the rotor.
      Once I figure it out I'll post back up for the info for all.
      Hi, my name is George & I'm a twisty addict!

      80G (Green paint(PO idea))
      The Green Monster
      K&N A/F, TC's fuse block, '81 oil cooler, TC's homemade 4-2 w/Mac Mufflers, Raptor 660 ACCT
      Got him in '04.
      bald tire & borrowing parts

      80SG (Black w/red emblems & calipers)
      Scarlet
      K&N A/F, TC's fuse block, WJ5, Shoei bags, Raptor 660 ACCT.
      Got her in '11
      Ready for the twisties!

      81H (previously CPMaynard's)
      Hugo
      Full Venturer, Indigo Blue with B/W painted tank.
      Cold weather ride

      Comment

      • #4
        Check those bolts while you're at it. If they're bent, I suppose that could be the problem. Still, it won't hurt to get after the rotors with the paper as well.
        Marty (in Mississippi)
        XS1100SG
        XS650SK
        XS650SH
        XS650G
        XS6502F
        XS650E

        Comment

        • #5
          The bent bolt thing makes no sense at all, the bolt is stationary and can't affect the moving parts at all. I have a warped/bent rotor on the spare front for the SG.

          You just need to figure out which one it is, I clamped the line one at a time on mine to do that. It's the right rotor that needs replacing. Sometimes you can just take it off and clean the mounting surfaces and cure it but that didn't work on this one. I can see the warpage in the contact marks.

          It's irritating but isn't really an issue unless you hit the front brakes at over 80 then the bars vibrate pretty bad.
          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

          • #6
            I just went through this issue about a month ago with my '80 special. front brakes pulsed when applied at just about any speed, more noticeable when coming to a complete stop. after having both rotors turned/trued and installing new pads still did it. replaced both caliper bolts and problem gone.
            I agree, doesn't really make sense but the new bolts cured the problem. for sure try that first, for about $2.00, before you start spending money on machine work and other new parts.

            Comment

            • #7
              If a bolt can make that light spot on the inside of the contact area on the front of this rotor I need someone to show me.

              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

              • #8
                Greg,

                Try deglazing that rotor with sandpaper or a paint stripping wheel. I have a warped rotor on my XS650 and it does not pulse.
                Marty (in Mississippi)
                XS1100SG
                XS650SK
                XS650SH
                XS650G
                XS6502F
                XS650E

                Comment

                • #9
                  Marty, thanks bro but deglazing won't take the obvious warp out. A glaze won't make it skip contact half the distance around.
                  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

                  • #10
                    Originally posted by BA80 View Post
                    Marty, thanks bro but deglazing won't take the obvious warp out. A glaze won't make it skip contact half the distance around.
                    No Greg, you're right. It will never take the warp out. I have fixed the pulsing sensation in both the bike and the car with garnet paper. I just thought I'd put that out there.
                    Marty (in Mississippi)
                    XS1100SG
                    XS650SK
                    XS650SH
                    XS650G
                    XS6502F
                    XS650E

                    Comment

                    • #11
                      The one thing I'd be concerned about with a warped rotor is excessive wear on the pad retainers (the stainless steel wear clips) and the caliper mount on the standards. The clips in particular are becoming unobtainium, and as-designed, any caliper movement is supposed to be minimal and gradual to account for pad wear.
                      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

                      • #12
                        Originally posted by crazy steve View Post
                        The one thing I'd be concerned about with a warped rotor is excessive wear on the pad retainers (the stainless steel wear clips) and the caliper mount on the standards. The clips in particular are becoming unobtainium, and as-designed, any caliper movement is supposed to be minimal and gradual to account for pad wear.
                        I'm not OK with the warped rotor. I'm going to replace it soon. I wanted to point out that a pulsing in the brake is more likely a glazed rotor than a warped one. Of coarse, when it's warped as bad as Greg's, all bets are off.
                        Marty (in Mississippi)
                        XS1100SG
                        XS650SK
                        XS650SH
                        XS650G
                        XS6502F
                        XS650E

                        Comment

                        • #13
                          Steve when you talk about the clips for the Standards being unobtanium they are $5.00 as a kit on Mikes XS. You get the spring clips and screw in one kit. Part #29-3200 At least I think that is what you were talking about.
                          http://www.mikesxs.net/products-101.html#products
                          To fix the problem one should not make more assumptions than the minimum needed.

                          Rodan
                          https://www.youtube.com/watch?v=khm6...liHntN91DHjHiS
                          1980 G Silverbird
                          Original Yamaha Fairfing and Bags
                          1198 Overbore kit
                          Grizzly 660 ACCT
                          Barnett Clutch Springs
                          R1 Clutch Fiber Plates
                          122.5 Main Jets
                          ACCT Mod
                          Mac 4-2 Flare Tips
                          Antivibe Bar ends
                          Rear trunk add-on
                          http://s1184.photobucket.com/albums/z329/viperron1/

                          Comment

                          • #14
                            Nice to know that these are now being reproduced.....
                            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

                            • #15
                              The ones for the Special are the hard to find ones.
                              2H7 (79)
                              3H3

                              "If it ain't broke, modify it"

                              ☮

                              Comment

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