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Twinpot Brake upgrade on 78 Skunk

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    I know 10.9 steel hardware is recommended for the calipers and brackets. I need to source the bolts that hold the rotor to the wheel hub. Should I use 10.9 steel or stainless for these?

    Edit: my bike has a thin plastic spacer between the hub and rotor (#16 in the diagram). I assume I ditch this and just use the metal spacer from the kit since the dual disc bikes don't have the plastic spacer. Correct?

    Do you guys use the "washers" (#15) on the rotor bolts as well?

    Last edited by hannibal; 08-13-2018, 05:10 PM.
    Jordan

    1977 Suzuki GS750 (My first bike)
    2000 Kawasaki ZRX1100
    1973 BMW R75/5

    Comment


      Re #15, I do , it locks the bolts in place.
      1982 Katana 1100, 1997 HD Ultra Classic, 1996 Buell S2T, 2002 BMW K1200RS, 1969 Royal Enfield Interceptor Triton project
      New project 1979 GS1000S
      Recently sold 1979 Honda CBX1000

      Comment


        Originally posted by 2whldreams View Post
        G
        The aftermarket now has cost effective alternatives for new rotors. Are there brand new (Asashi?) rotor, rotor carrier, and buttons that can be recommended that don't require drilling modifications? Part numbers would be helpful. Ebay is such a crap shoot.
        Thank you for your time
        Nope. All of them need drilling to some degree.
        1980 GS1000G - Sold
        1978 GS1000E - Finished!
        1980 GS550E - Fixed & given to a friend
        1983 GS750ES Special - Sold
        2009 KLR 650 - Sold - gone to TX!
        1982 GS1100G - Rebuilt and finished. - Sold
        2009 TE610 - Dual Sporting around dreaming of Dakar..... - FOR SALE!

        www.parasiticsanalytics.com

        TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

        Comment


          Entering comments in quote below with a ****

          Originally posted by hannibal View Post
          I know 10.9 steel hardware is recommended for the calipers and brackets. I need to source the bolts that hold the rotor to the wheel hub. Should I use 10.9 steel or stainless for these?

          **** I have used Stainless before but made sure it was a decent A2-70 grade. 8.8 or 10.9 regular steel would be better.

          Edit: my bike has a thin plastic spacer between the hub and rotor (#16 in the diagram). I assume I ditch this and just use the metal spacer from the kit since the dual disc bikes don't have the plastic spacer. Correct?

          **** CORRECT

          Do you guys use the "washers" (#15) on the rotor bolts as well?

          **** YES

          1980 GS1000G - Sold
          1978 GS1000E - Finished!
          1980 GS550E - Fixed & given to a friend
          1983 GS750ES Special - Sold
          2009 KLR 650 - Sold - gone to TX!
          1982 GS1100G - Rebuilt and finished. - Sold
          2009 TE610 - Dual Sporting around dreaming of Dakar..... - FOR SALE!

          www.parasiticsanalytics.com

          TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

          Comment


            Thanks for the answers.

            One more question: is there any reason a Suzuki piston and seal rebuild kit (from a GS500 or GSX1100G) wouldn't work on a Kawasaki caliper? I tore down my Kawasaki calipers to inspect them and was planning to replace the seals and dust seals, but at least one of the pistons has some minor pitting. The Kawasaki piston and seal set is about $50 per piston ($100 per caliper), and the Suzuki set is under $40 per caliper. The calipers are identical (as far as I can tell), so the Suzuki kit should work in the Kawasaki caliper, right?
            Jordan

            1977 Suzuki GS750 (My first bike)
            2000 Kawasaki ZRX1100
            1973 BMW R75/5

            Comment


              Should be identical parts...
              Good to know the Kaw stuff is for rich people & Mr Suzuki prices parts for the common people, THANKS!
              '77 GS750 920cc heavily modded
              '97 Kawasaki KDX220R rugged terrain ripper!
              '99 Kawasaki KDX220R​ rebuild in progress
              '79 GS425stock
              PROJECTS:
              '77 Suzuki PE250 woods racer
              '77 GS550 740cc major mods
              '77 GS400 489cc racer build
              '76 Rickman CR1000 GS1000/1100
              '78 GS1000C/1100

              Comment


                Why should they be identical?
                1982 Katana 1100, 1997 HD Ultra Classic, 1996 Buell S2T, 2002 BMW K1200RS, 1969 Royal Enfield Interceptor Triton project
                New project 1979 GS1000S
                Recently sold 1979 Honda CBX1000

                Comment


                  Thanks Chuck. Just wanted a sanity check.

                  Originally posted by johnod View Post
                  Why should they be identical?
                  Tokico makes the calipers and Kawasaki and Suzuki both use them. The parts diagrams are identical. I assume the caliper components are made by Tokico (or likely a Tokico supplier) but Kawa and Suzuki package and price them differently.
                  Jordan

                  1977 Suzuki GS750 (My first bike)
                  2000 Kawasaki ZRX1100
                  1973 BMW R75/5

                  Comment


                    I see, did not know that, good to know. Thanks.
                    1982 Katana 1100, 1997 HD Ultra Classic, 1996 Buell S2T, 2002 BMW K1200RS, 1969 Royal Enfield Interceptor Triton project
                    New project 1979 GS1000S
                    Recently sold 1979 Honda CBX1000

                    Comment


                      I'm not sure if this has been discussed before in this thread but I have searched the best I can and can't find anything. Basically what I want to know is if there is any benefit to the twin-pot caliper on only one side? I'd kinda like to keep the look of the single rotor with spokes on the 78 Gs750 but would also like better braking performance. Common sense tells me that there should be some improvement with a larger swept area but is it worth it? If so how about MC size for a single caliper? Stock rotor or aftermarket?
                      The current garage:
                      1978 GS750
                      1975 GT750M
                      1984 CB700SC
                      1982 XJ650 Seca Turbo
                      1975 RD250 - 350 conversion

                      Comment


                        I'm sure there will be a benefit even with just the one caliper.
                        1982 Katana 1100, 1997 HD Ultra Classic, 1996 Buell S2T, 2002 BMW K1200RS, 1969 Royal Enfield Interceptor Triton project
                        New project 1979 GS1000S
                        Recently sold 1979 Honda CBX1000

                        Comment


                          Yes you will definitely benefit with just one side on a 750, as you will be getting twice the swept area and be going from 295 mm rotor up to 310mm. You need a 98 - 99 CBR900RR rotor to do this. And you just need the caliper bracket, you do not need the rotor spacer as that rotor already has 23 mm offset.

                          I would definitely recommend getting a good brand new set of pads and a stainless steel brake line if you are just going single-disc, you will want every bit of performance you can get. This setup is plenty adequate for a GS 550 which is about 50 pounds lighter than your 750. If you are riding a 750 really aggressively and on very twisty roads, or if you have a lot of big hills around, a dual disk would still be beneficial to keep them running cooler and not have to suffer from anywhere near the amount of brake fade when the rotor(s) get hot.
                          On a race bike, dual discs are also beneficial as then you have the fork twisting forces somewhat equalized since both fork legs are trying to twist under the braking force.
                          '77 GS750 920cc heavily modded
                          '97 Kawasaki KDX220R rugged terrain ripper!
                          '99 Kawasaki KDX220R​ rebuild in progress
                          '79 GS425stock
                          PROJECTS:
                          '77 Suzuki PE250 woods racer
                          '77 GS550 740cc major mods
                          '77 GS400 489cc racer build
                          '76 Rickman CR1000 GS1000/1100
                          '78 GS1000C/1100

                          Comment


                            Originally posted by Chuck78 View Post
                            Yes you will definitely benefit with just one side on a 750, as you will be getting twice the swept area and be going from 295 mm rotor up to 310mm. You need a 98 - 99 CBR900RR rotor to do this. And you just need the caliper bracket, you do not need the rotor spacer as that rotor already has 23 mm offset.

                            I would definitely recommend getting a good brand new set of pads and a stainless steel brake line if you are just going single-disc, you will want every bit of performance you can get. This setup is plenty adequate for a GS 550 which is about 50 pounds lighter than your 750.
                            Thanks for the info, I think I'm going to go for it and see what happens. I already have a cool set of (very expensive) blue anodized stainless lines. I'm not really looking for all out performance at the moment since my exhaust limits my ground clearance anyway. I just want a little better brakes for an extra margin of safety and for the occasional spirited riding I do. Also I'm in florida so all the roads are all straight
                            How about MC bore size? I've got a 14mm aftermarket MC for the stock system. What is the piston volume of the Ninja caliper?
                            The current garage:
                            1978 GS750
                            1975 GT750M
                            1984 CB700SC
                            1982 XJ650 Seca Turbo
                            1975 RD250 - 350 conversion

                            Comment


                              The Ninja MC is a 14mm (aka Ninja 250) if you use one or 5/8" (aka bigger ninja, concourse etc) if you use two...
                              1980 GS1000G - Sold
                              1978 GS1000E - Finished!
                              1980 GS550E - Fixed & given to a friend
                              1983 GS750ES Special - Sold
                              2009 KLR 650 - Sold - gone to TX!
                              1982 GS1100G - Rebuilt and finished. - Sold
                              2009 TE610 - Dual Sporting around dreaming of Dakar..... - FOR SALE!

                              www.parasiticsanalytics.com

                              TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

                              Comment


                                I usually recommend using a ninja 250, GS500, or Bandit 400 master cylinder for the single disc setup, & I believe those are all 9/16"? It is basically the same as GS stock single and dual disc master cylinder bores. It was 5/8" for the dual. Funny thing is, despite being metric parts, the bore size i recall seeing cast into the parts in inch sizes on some of them! Sort of like inch sized tires worldwide, except for newer bicycles, & car/truck widths being in millimeters (but not rim diameters still, standard is in inches!)
                                '77 GS750 920cc heavily modded
                                '97 Kawasaki KDX220R rugged terrain ripper!
                                '99 Kawasaki KDX220R​ rebuild in progress
                                '79 GS425stock
                                PROJECTS:
                                '77 Suzuki PE250 woods racer
                                '77 GS550 740cc major mods
                                '77 GS400 489cc racer build
                                '76 Rickman CR1000 GS1000/1100
                                '78 GS1000C/1100

                                Comment

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