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Using a Harley Rear Master Cylinder

Written by Danny Harder (hardone2get)   
Sunday, 01 November 2009

Yamaha Road Star using Harley Master Cylinder

Items Needed:

  • Kelsey Hayes type master cylinder: L 1979-1983 Harley FX or 1980-1981 XL Sportster Product Link
  • 3/16”x 1” flat stock approximately 4” long.
  • 2 bolts 5/16”x 2 ½”
  • 2 5/16”chrome acorn nuts
  • 1 5/16” x 24 banjo bolt
  • 1 5/16” solid rod (purchase at hardware store)
  • 1 brake light switch for 67-79 Chevy Nova OEM# 1261219
Chevy Nova Brake Light Switch

Getting Started:

  1. Remove banjo bolt from stock master cylinder and tie brake line up as high as possible with a zip tie. This will avoid too much air in the brake line.
  2. Remove 2 Allen head bolts holding the floor board assembly, remove complete assembly and take to work bench.
  3. Remove master cylinder and reservoir from floor board assembly.
  4. Using a cut off wheel in a 4” or 4 ½” grinder, cut off the bolt on portion of the bracket (as indicated in the picture below.)

    Yamaha Road Star Rear Brake Cylinder Mounts

  5. Grind the welds holding the stock brake light switch bracket. Be careful as you are going to need to weld this back on.
  6. Take your 3/16”x 1” flat stock and hold it up to your new master cylinder to mark for holes and length.
  7. Cut to length (approx. 3 ½”), drill holes with 21/64” bit, which is just slightly larger then 5/16”, this will allow you to mount and move slightly if your holes are not perfect.
  8. Weld your new master cylinder bracket onto your pedal assembly. You want to keep the back hole of the new bracket in approximately the same place as the old one was.
  9. Weld your brake light switch mount just below the curve in the steel of the pedal assembly, as shown in picture below.

    Yamaha Road Star Brake Assembly Modified for Harley Master Cylinder

    (Hint) Use your new brake light switch in the mount before you weld to make sure that you will have it correctly positioned. Here is another picture of it completed to give you an idea of location. Do Not Weld Bracket with Switch attached!!!!

    Yamaha Road Star Brake Assembly With Harley Master Cylinder Mounted

    As you can see from the picture above, the brake light switch needs to be positioned so that the center button is pushed in when the pedal is at it’s normal upright position.

  10. After welding, clean up everything, sand and paint black.
  11. Take your 5/16” solid rod and place inside the master cylinder (as seen above). You are measuring the rod to mount just like the stock one. Make sure the pedal is all the way up and the bracket to which the rod connects is standing straight. Measure and mark, then cut to length. Next place the rod in a cordless drill. While you run the drill use a bench grinder and round out the tip. Once you have your shape, use finer sand paper and hold the sand paper in your hand and wrap around the tip and run the drill again to really smooth out the tip!

    Yamaha Road Star Mod - New Brake Pushrod

  12. Using a ¼” x 20 die, cut an approximate 1-1 ¼” length of threads onto the other end of the push rod.

    Yamaha Road Star Brake mod - new pushrod

  13. Remove master cylinder and install the rod into master cylinder and connect the other end to the bracket using a ¼” nut. Note! I had to grind the 2 sides of the ¼” nut in order to make it fit into the small bracket to which it attaches. Next mount the master cylinder back onto the pedal assembly. Adjust the rod to where there is no slack between pedal & master cylinder push rod and then tighten the outer nut down to the bracket.
  14. Mount assembly onto the bike, but do not mount the brake line yet!!!
  15. Fill the master cylinder with brake fluid.
  16. Take one finger and place it over the master cylinder end where the brake line would hook up and keep pressure with your finger. Slowly push the pedal down but not all the way! Pump the pedal lightly till you feel some pressure. Let off and then just as you start to push the pedal pull your finger away and allow the fluid to escape. Before the pedal hits bottom put your finger back over the end and let off the brake pedal. Do this procedure a few times to make sure you don’t have any air.
  17. Connect the brake line.
  18. Now bleed the caliper in the same manner as the master. Push on the pedal as you open the bleeder and close before the pedal bottoms out. If you don’t get any air, your done!!!

Yamaha Road Star with Harley Master Cylinder

Yamaha Road Star with Harley Master Cylinder - Front

Yamaha Road Star with Harley Master Cylinder - Front2

Yamaha Road Star with Harley Master Cylinder Top

Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

Discuss this article on the forums. (6 posts)

DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.

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  Comments (4)
Written by Starkruzen, on 01-25-2011 18:14
What is the advantage of this mod other that looks?
Great Idea
Written by rjb0zy, on 05-31-2010 07:27
This is nice work. It will be even nicer when you dispose of that stupid brake light switch all together. Just replace the stock banjo for a banjo switch. Then you will have nothing there but the Master and two wires in the end. Just connect and go ... ;) Stay On Top R.j
Nice and Clean
Written by Randysgym, on 01-02-2010 09:33
I thought the stock setup was just fine (with chrome cover), but you have shown me 'the light'! This looks like a much more compact and prettier method. Plus, it eliminates that damn, stock, rear brake-light, switch setup that I tend to brake when I remove the right-side floor-board for pipes or generator or cams or whatever. THANKS; I'm putting this on my to-do list.
Written by Crazyron1369, on 11-02-2009 10:12
Great project I'm going to do mine this winter.

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