TECH: Make a tiny brake fluid reservoir

[edward]

A few have asked so here ya go.
You want a front brake but you also like the minimalist look up front. Follow me down the rabbit hole.
I say rabbit hole because if you’re going to change up your master cylinder during this process, you’ve gotta make sure your get the correct size master cylinder. I kinda cheated and used the Internet to determine what other master cylinders worked with my Buell’s six piston caliper. The stock master cylinder was massive and the replacement (Nissin) was relatively small and inexpensive.



For simplicity’s sake we’ll assume you only need to replace the reservoir. If you don’t know how to bleed brakes, stop here and learn before going forward.



1. Remove reservoir
2. Remove the stem (part #13159 in the diagram)
3. Most stems, at least on the Nissin master cylinder, are L shaped
4. Cut the stem at the elbow
5. Ensure the cut is clean and there are no plastic filings waiting to get jammed into your master cylinder
6. Install the stem
7. Don’t replace the dust cover (part# 49016a in the diagram). You can install the dust cover but it will leave you little room to install the clear reservoir tubing. I tried it this way (see first picture) only to have it fall to the ground after a hand smack.
8. Connect 6” of clear tubing to the stem. You’ll be cutting the tubing down but the extra few inches will prove valuable during the brake bleeding process
9. Secure tubing with safety wire or a small zip tie
10. Fill tubing with brake fluid and bleed brakes
11. Find a stainless allen head bolt that is a bit bigger than the diameter of the clear tubing. I made a nice aluminum a cap for version one (see first picture) of my mini reservoir set up but it would pop off now and then. The threaded bolt will allow any fluid or air to escape under pressure while keeping water out of your master cylinder. I put the bolt in a lathe and turned down the top. Since most allen head bolts are etched on the side, it makes it easier to twist into the clear tubing.
12. Cut the clear tubing and install the cap.



I've got several thousand miles and rain storms on this set up. Works great.

[edward]

Credit: I got the idea from a Bling Cycles bike and Tha Nutz’s Mr. Roboto as seen below.

[framus]

At least when the brake fluid starts breaking down that hose, it's cheap and simple to replace.

[edward]

At least when the brake fluid starts breaking down that hose, it's cheap and simple to replace.

It's DOT 5. No worries yet.

[billdozer]

Good, simple tech Ed, thanks for posting this. We did the same thing on BFJosh's Triumph and it's been working fine ever since.

[Toecutterp]

Cool set up, i've been running the same set up for awhile. I got the idea from road race bikes. Some of us run the same set up on the rear to save a little weight. I would never run it on my front brake on my race bike but my choppers good to go.

[edward]

Bling


DBBP


Greg's Customs

[Flatironmike]

good stuff, Ed. thanks for sharing.

[deadbird]

cool. I'm gonna try this.

[Toecutterp]

It works great i've been doing it for a few years and have had 0 problems

[cafcustoms]

Hi.
You mention the importance of matching the size of the master cylinder to the caliper, which I understand.
My build has a GMA front caliper which has to be paired with a 5/8 master cylinder.
Can anyone suggest, or have any experience with a replacement radial master for a Harley 5/8"?

[Homebrew]

This is something I have been wondering about. Thanks for the info. I want to do this on my Sporty.

[KingPynn]

you guys just saved me like 200 bucks thanks, great tech

[cafcustoms]

Can confirm that a 5/8" Nissin master cylinder fitted as standard to Kawasaki ZX6 up to about
'07 can be used. I'm matching mine to a GMA Model B caliper. I'll post some pics when I'm done.

[ARBY]

OK. I'm almost ready to give this a try. But what are yooz guys doing for brake lines and clutch cables??? I doubt the japper controls are gonna hook up with Harley components.

[edward]

OK. I'm almost ready to give this a try. But what are yooz guys doing for brake lines and clutch cables??? I doubt the japper controls are gonna hook up with Harley components.

i like the goodridge ebony stainless lines. look like old hoses but you get modern performance.


they use AN-3 fittings. great for when you need address crazy angles. the have the straights too:

[ARBY]

That's what I'm looking for. Thanks much.

[TimB1640]

ok i see what you have done but my questionto you now is, you said you used the internet to find out what master cylinder size would work for you. ok but now can you tell us where or explain how we find out that info ? thank you

[TimB1640]

where do you find the little caps?

[crass]

the original poster is using a stainless steel allen bolt w/head shaved down
I'm sure a plain old SS allen bolt will work, get it at any fastener shop..
just make sure to bring your tube with you to make sure it's fatter than the tube


however, I'm largely confused as to the majick behind chosing the proper size master cylinder so that the breaks actually work.