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1979 sf special front brake m/c size

Discussion in 'The Garage' started by gray am I, Mar 21, 2019.

  1. gray am I

    gray am I XS650 Enthusiast

    mechanic doing some work on my bike commented that he thought that the nissin 11/16 front master on my special was too large and he thought it should be a smaller size is this the original sizing for this Australian twin disc special or is he right?
     
  2. XSLeo

    XSLeo XS650 Guru Top Contributor

    11/16 bore is 17.46 mm. I think that's too big. The stock 14 mm bore as used on the single caliper brakes here in the US work ok for a single but an 11 of 12 mm works much better. They do work well with a dual disc set up.
    I have two bikes set up with dual disc. The 75 uses 5 mm thick slotted rotors. The 81 uses 7 mm slotted rotors.
    The calipers and rotors are stock Yamaha parts.
    Upgrading the brake lines from the stock rubber to braided stainless steel lines is well worth the cost. Rubber has a lot of stretch to them. The braided lines don't. All your lever effort goes to operate the brakes instead of losing part to swelling the rubber lines.
    Leo
     
    peanut and grizld1 like this.
  3. I changed my 79 sf to a 12mm master and braided lines, mechanic who did the roadworthy on it reckoned they were the best brakes he'd seen on a 650.
     
    peanut likes this.
  4. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    I think both of those statements are true.
    Was running this
    madness front brake first version.jpg
    with the stock US spec single disk 14mm MC and it worked well.

    Changed to this set up
    brake detail.jpg
    losing about 8 pounds! of unsprung rotating mass. Still using the 14mm MC. :thumbsup:
    Aftermarket 14mm MC's are dime a dozen and with SS lines should be a very noticeable and pleasant improvement in brake feel and control.
     
    peanut, grizld1 and aldo5468 like this.
  5. aldo5468

    aldo5468 Redleg XS650.com Supporter

    What rotors are those? Very nicely done!
     
  6. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Later Yamaha sport bike FZ600 to 1000cc 89-93 something like that. Flea bay, they are either the right ones or a totally different design. You need to use 6 to 7mm spacers tween the flange and rotor to line up with the stock caliper.
    DSCN0482.JPG DSCN0479.JPG brake rotors spacer poa 013.JPG
     
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  7. aldo5468

    aldo5468 Redleg XS650.com Supporter

    Stock caliper looks really good after stripping the OEM black paint!
     
    gggGary and peanut like this.
  8. gray am I

    gray am I XS650 Enthusiast

    This master cylinder was on the bike when I purchased it. xs 650 master cylinders seem to come in all different sizes so I assumed this larger diameter was an original fitment for the Australian twin disc models. Can anyone tell me what the correct original diameter for my 79 special should be?
     
  9. 18mm on my 79 Australian delivered twin disc.
     
  10. gray am I

    gray am I XS650 Enthusiast

    thanks my 79 is a nissin 11/16 (17.46). I thought it was the original so some time back I had it resleeved in stainless as I couldn't find another,
     
  11. Yes, my original one is the same, just checked.
    I lead you astray with my comment above sorry, I did buy a 12mm aftermarket one but did not like the way it sat on my bars, then ended up getting the 16 mm one from Geoffs Xs in Sydney.
     
    gggGary likes this.

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