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GS750DB front brake specs

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    GS750DB front brake specs

    Does anyone out there have any knowledge of how the parts for the double-disc 1977 GS750 (DB) differed from the single disc model (B)?

    I have a 77 B - single disc, wire wheels, 300mm disc, Tokico caliper with a 43mm piston.

    Having done a complete rebuild, I thought I may as well upgrade to the double-disc set-up. However, tracking down information on the DB has proven difficult - none of the parts fiches even list the possibility of a right-side brake, yet it is undoubtably a genuine factory model.

    First step is to obtain a right-side fork leg that has the cast bosses for the caliper mount - not present on the B. There's no parts listing for one, and I've never seen any for sale - so the answer seems to be to use those from a double-disc E model.
    However, because the E models use 275mm discs the bosses are placed lower on the fork leg to bring the caliper down to the disc - meaning that the 300mm discs can't be used.

    A right-side caliper was hard to find until I realised that the 79 850G used the same calipers, but with a 38mm piston - they're easy to get.

    Back to the question - did the DB use the same fork legs as the later E model, and also use the smaller discs; or did it have its own specific right fork leg with high bosses to allow for the larger discs?

    Given that the E model (cast wheels) did not exist when the B or DB was released, it was not a question of parts sharing at that time - the parts would have been specific to that model - would Suzuki have gone to the trouble of manufacturing different discs for the same bike?

    The 'simple' answer (aargh, more money!) is to get a set of 275mm discs, but I am still curious.

    (I initially fitted one of Salty Monk's excellent twin-pot conversions, but I found that the regulations here in New Zealand are that such modifications must be certified before registering the vehicle - involving transporting it 100 kilometres, leaving it for a day, and $500!)
    '77 750B - owned it since '79
    '78 750C
    '80 850G
    '70 TS250-2 - doing the rebuild
    '75 Yamaha XS650B
    '03 Ducati ST4S

    #2
    The DB used the same form legs as the E (or G for that matter). Any of the E or G discs will fit including later slotted type. Similarly E calipers will plug straight in. Best would be the 82 onwards from the 850G. GL calipers won't fit because of the leading axel offset.
    79 GS1000S
    79 GS1000S (another one)
    80 GSX750
    80 GS550
    80 CB650 cafe racer
    75 PC50 - the one with OHV and pedals...
    75 TS100 - being ridden (suicidally) by my father

    Comment


      #3
      Thanks Hampshire - that does sound logical - nice to get it confirmed! No doubt other DB owners can confirm that their discs are 275mm.
      To set up up Salty Monk's twin-pot set-up, I had a set of E fork legs already installed, and I have a set of those 79 850G Tokicos that are the same model as the 77's - (if I can't do the twin-pot set-up I'll go for 'original', 'stock', 'standard', or whatever you want to call it).

      I've got one 275mm disc from somewhere that matches the 'spoke' pattern of the original 300mm disc, and a couple of E discs with plain 'spokes', so something will fit!
      '77 750B - owned it since '79
      '78 750C
      '80 850G
      '70 TS250-2 - doing the rebuild
      '75 Yamaha XS650B
      '03 Ducati ST4S

      Comment


        #4
        They are all 274mm with the exception of the single disk models which are 296mm from memory.
        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


          #5
          I did something similar on mine.
          I had a set of single-braked fork legs from a 1000C (iirc) which had excellent stanchions, and used a set of dual-braked lowers on them from another 1000.
          The (rebuilt) 80-onwards calipers from the 850 fitted straight on, and allied with good Carbon Lorraine pads and a NT650V 5/8th master cylinder, the brakes are now excellent.
          ---- Dave

          Only a dog knows why a motorcyclist sticks his head out of a car window

          Comment


            #6
            Originally posted by Grimly View Post
            The (rebuilt) 80-onwards calipers from the 850 fitted straight on, and allied with good Carbon Lorraine pads and a NT650V 5/8th master cylinder, the brakes are now excellent.
            C.L. makes break pads for our old GS’s? I’ll have to look into that. I like their race pads on my SV.
            1979 GS850G
            2004 SV650N track bike
            2005 TT-R125 pit bike
            LRRS #246 / Northeast Cycles / Woodcraft / Armour Bodies / Hindle Exhaust / Central Mass Powersport

            http://s327.photobucket.com/albums/k443/tas850g/

            Comment


              #7
              Originally posted by tas850g View Post
              C.L. makes break pads for our old GS’s? I’ll have to look into that. I like their race pads on my SV.
              They certainly did, but they're NOS by now. I just lucked into a stock of them a few years ago.

              I'll dig out a part number....

              They are S1 type
              No 2694S1 Sintered "C685" compound for normal road-going discs.
              I recall digging around for info when I got them and they've been superceded by newer materials, which might be why these were left on the shelf.
              Whatever the reason, once I bedded them in they were the best brakes this bike's ever had. They only needed re-bedding when the bike was laid up for a year, and after that they've been great again. I'm not all that heavy on the brakes so can't really say if they are shortening the life of the discs or not. Some say they do, but meh.
              Last edited by Grimly; 10-31-2019, 05:00 PM.
              ---- Dave

              Only a dog knows why a motorcyclist sticks his head out of a car window

              Comment

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