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And, Here, We, Go...
8,017 Posts
Discussion Starter · #1 ·
I just copied this, critique it please:

Brake Bleeding Basics

Brakes that work, and work well, are an absolute necessity on motorcycles designed to exceed most interstate speed limits in first gear alone. Still, hardly a day goes by that we don?t witness the results of brake system neglect, ranging from mushy levers and brake fade all the way up to brake failure and lockup. Sadly, most of these problems could have been easily averted for the price of a bottle or two of brake fluid and a few minutes time every few months.

As a general rule, performance motorcycles are designed to use DOT 3, 4, or 5.1 fluids ? all glycol based. The performance advantages of glycol-based fluids make them the only real answer in hydraulic systems where consistent lever feel and action are mandatory. However, glycol-based fluids come with a price, as they are easily degraded by exposure to atmospheric moisture and ultraviolet radiation (light). While there are steps that can be taken to minimize these factors, the only way to reliably keep your hydraulic brake system in tip-top shape is to routinely flush, bleed, and replace your brake fluid.

How often is often enough? For street-driven motorcycles, we recommend changing brake fluid and bleeding the system at least every 6 months. On race bikes, we recommend doing so before each event!

In our experience, the biggest stumbling block to routine brake system maintenance is the process of bleeding air from the system. On the surface, this would appear to be a relatively simple procedure, but as anyone who's had a 'problem bike' will attest ? it can be far from simple at times! This is especially true when starting with a dry brake system, as when changing lines.

We won't attempt to rehash the basic procedures of bleeding. There simply isn?t a lot to say on the subject that hasn?t been already been said. But there are a few tricks of the trade that we?ve found to be of benefit:
  1. ALWAYS start with a freshly opened bottle of fluid. Glycol fluids are extremely hydroscopic, which means they take on moisture from the atmosphere. Absorbed moisture lowers a brake fluid's boiling point, which results in brake fade. Even if you?ve closed a bottle tightly, the air trapped within can contain enough moisture to contaminate the contents. It's best to purchase small bottle of fluid and open one each time you service your brakes, rather than keep one large one on the shelf.
  2. Use a vacuum pump. The Miti-Vac is one example, but there are plenty of other similar pumps on the market that work equally well. By using a vacuum pump to draw fluid from the bleeder screws, you can expedite the process and all-but-guarantee you won?t accidentally re-introduce air into the system. If you're serious about brake bleeding, a vacuum pump is a valuable commodity you will not regret purchasing!
  3. Tap, Tap, Tap. Using a screwdriver or wrench to quickly & lightly tap brake system components, such as the lines, calipers, and master cylinder, can help move small air bubbles up and out of the system. Next time you're drinking a carbonated beverage, examine the gas bubbles clinging to the edges of your glass. Air in your brake system does the same thing. Tap your glass. See the bubbles rise? The same thing happens in your brake system. Tap, tap, tap.
  4. Think like a bubble. It may sound silly, but keeping in mind the simple fact that air bubbles rise can save you a lot of time bleeding brakes. Particularly in OEM arrangements, there are often brake line junctions where air can be trapped. Sometimes, in order to get a good bleed, you'll need to temporarily remove and re-align components in order to give air a straight shot to the top of the system.
  5. Work up from the bottom. Start by bleeding the calipers. Then bleed at the master cylinder. Air rises. You should also rise up as you work to bleed the system.
  6. Collapsing pistons. In some systems, air gets trapped behind the caliper pistons, which can lead to serious frustration! It often helps to remove the calipers, one at a time, and push the pistons all the way back into the caliper body. Make sure to keep an eye on the level of fluid in your reservoir as you do this, as it can overflow if you're not careful. When doing this, we usually siphon off most of the fluid in the reservoir first, and then refill to the top before pumping the brakes.
  7. Bleed at the master cylinder. Since air rises, this is usually the final and most effective step to bleeding the system. Most of the newer radial master cylinders are now incorporating bleed screws, which make this step a breeze. But if you don't have such luxuries, you can either lightly crack the banjo bolt at the master cylinder while maintaining lever pressure (keep a rag underneath to catch fluid), or purchase a banjo bolt with a bleeder screw incorporated. The latter is definitely our option of choice.

90 Posts
anthony said:
decent write up, but lacking a few things.

let me see what i can put together for you in a step-by-step procedure.
That would be great! I am looking to swap out my brake lines with the stainless ones I have laying around
Just out of curiosity, what few things is this article lacking? So I'll know what to look for.

1,630 Posts
As with all of my little "How-to" posts, this is my method of doing this procedure. This is what works for me, my bike, my friend's bikes, and my customer's bikes. Your method may differ, so take what you want from it.

Tools Needed:
8mm open end wrench
NEW bottle of DOT 3 or DOT 4 brake fluid
Empty container (like an old drinking cup)
Clear tubing that fits snug over the bleeder screw
Miti-Vac brake bleeder

1. You will need to drain the old fluid first, so attach the tubing to the left caliper bleed screw, and put the other end in the empty container
2. Take the cap off of the brake reservior, and remove the rubber diaphragm
3. Open the bleed screw with your wrench, then squeeze and release the brake lever until all the fluid is drained out
5. Disconnect the tubing and empty container, leaving the bleed screw open
4. Attach the Miti-Vac to the left brake caliper bleed screw
5. Fill the reservior with the new brake fluid, but don't put the cap back on yet (be very careful nothing falls in there though!)
6. Have a friend (or you if you have really long arms...) continuously refill the reservior while you pump the Miti-Vac
7. Stop pumping when you start to see brake fluid coming out
8. Close the left caliper bleed screw with the Miti-Vac still attached
9. Be sure the fluid level is full in the reservior, and now put the rubber diaphragm back in and the cap on, making sure the rubber diaphragm is collapsed, not extended
10. Pump the Miti-Vac until you see about 20psi worth of pressure in the gauge, crack open the bleed screw, wait a second or 2, and close the screw again
11. Check the lever pressure (you probably won't have any yet)
12. Move on to the right caliper bleed screw
13. Repeat steps 9-11
14. If so equipped, move to the master cylinder bleed screw and again repeat steps 9-11
15. Once there is decent pressure in the lever, move back to the left caliper bleed screw without the Miti-Vac
16. Attach your tubing and empty container to the left caliper bleed screw once again
17. Refill the brake reservior, then pump the brake lever to build up pressure
18. While squeezing the lever forcefully, crack open the bleed screw quickly. The lever will hit the clip-on, but this is good. DO NOT LET GO OF THE LEVER!!!
19. Close bleed screw after a second or 2
20. Move on to the right caliper bleed screw and repeat steps 17-19
21. Move on to the master cylinder bleed screw (if so equipped) and repeat steps 17-19
22. By this time you should have sufficient lever pressure, and all air should be out of the system.
23. If not, repeat steps 17-19 until you do, moving from left caliper bleed screw to right caliper bleed screw to master cylinder bleed screw until sufficient pressure is acquired

Be sure to test the brakes first before riding the bike
Be sure to clean all brake fluid off of the bike as soon as possible
Always make sure the reservior is full
Do not release pressure on the lever until the bleed screw is completely closed

907 Posts
Same shit I said in the other thread. Pull your brake lever in (enguaged position) and pull the cap off of it. Fill it up to the top, place a cover over it so It dont get dirty. Let it sit over night for about 8 hours or so if not over night. And let all the air bleed its self out of the line. It works every time.

Use a dry erase marker or a pencil so you dont leave permanemt marks. But mark where the level is and I guarantee you will see a difference the next day IF you need to bleed em.

Avplayer said:
actaully i have this kit....but i got it last year from harbor freight for $35 shipped

I always brake my harbor freight tools

Senior Member
1,560 Posts
Plastic Cup Politics said:
aha! I actually was browsing harbor freight earlier today... that thing will get the job done? That place doesn't exactly sell "quality" tools.
well to be honest u don't "need" the kit, u can do it w/o it but u need another person and it take a whole lot longer... i can bleed my brakes in less than 10 min

Brahptimus Prime
23,504 Posts
Well I know HOW to bleed brakes, the old fashioned way and the new way. I PREFER to use a vacuum bleeder. I already have a Snap-on bleeder, but I don't have access to a compressor anymore. So that's why I'm asking about the manual tools.

And Jamie, I am replacing my pads and lines so that's the only reason I am going to have to bleed them after the install.
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