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YBR125 Brake Bleeding

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sparkywilliam...
Scooby Slapper



Joined: 27 Jan 2010
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PostPosted: 10:53 - 12 Oct 2010    Post subject: YBR125 Brake Bleeding Reply with quote
Hi,
I'm trying to get my front brake caliper to work again after stripping it out and cleaning it.

Obviously air has got into system as i let the fluid run very low when i was cleaning caliper.

Ive reassembled everything and have filled up master cylinder with fresh fluid (i put it in after lifting up the small black rubber seal-is this correct?) and refiited top plate.I have attached rubber hose to bleed nipple and the other end into glass of brake fluid.I've losened nipple and i'm squeezing brake but its all soft and i can't understand how to create a pressure again?
The fluid doesn't look like its leaving the master cyclinder container and going down the tube into the caliper.
I put my hands up,im stuck.What's the secret.?
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.....
Quote Me Happy



Joined: 15 Jan 2005
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PostPosted: 11:06 - 12 Oct 2010    Post subject: Reply with quote
Loosen the nipple as you squeeze the brake lever, then close the nipple before releasing the lever. Repeat until bled. Don't refit the top plate on the reservoir until the system is bled.

Try having a search on Youtube, there should be something on there showing you how it's done.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 11:16 - 12 Oct 2010    Post subject: Re: YBR125 Brake Bleeding Reply with quote
sparkywilliams wrote:
Hi,
I'm trying to get my front brake caliper to work again after stripping it out and cleaning it.

Obviously air has got into system as i let the fluid run very low when i was cleaning caliper.

Ive reassembled everything and have filled up master cylinder with fresh fluid (i put it in after lifting up the small black rubber seal-is this correct?) and refiited top plate.I have attached rubber hose to bleed nipple and the other end into glass of brake fluid.I've losened nipple and i'm squeezing brake but its all soft and i can't understand how to create a pressure again?
The fluid doesn't look like its leaving the master cyclinder container and going down the tube into the caliper.
I put my hands up,im stuck.What's the secret.?


I think you're going to be there a long time. If you can't even get fluid moving in the tube, then you have run SERIOUSLY low of fluid and you're effectively bleeding the system from the start again. Luckily its a single caliper single line system so it shouldn't be as hard as some bikes, but brake bleeding is one of my pet hates and it takes ages.

First off, you need to remove the reservoir cap and all of the cap seal gubbins from the top of the reservoir. Then you've got three options:

1.) The traditional method which you are currently using. As Joe said, loosen the nipple with pressure on the brake lever and tighten it again before you run out of lever travel completely. This will take a long time and is very messy. Make sure you don't let the fluid level drop below MIN under any circumstances.

2.) Using a compressor and a vacuum tool. This is the way I do it, because I've got a compressor and a brake bleeding tool. Takes a few minutes and makes very little mess.

3.) Using a syringe to push fluid up through the line. Fill a large medical syringe with brake fluid, and using a piece of tube to connect it to the open bleed nipple (with a ring spanner on it so you can tighten it again) force fluid up through the line until no more air bubbles appear. It is good to start the process with low fluid first so that the reservoir doesn't overflow.

Other than that all I can say is it can be a total bitch of a job and it always takes ages.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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Quote Me Happy



Joined: 15 Jan 2005
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PostPosted: 11:20 - 12 Oct 2010    Post subject: Reply with quote
I recently did the reverse bleed method on a clutch (same principle) and it worked brilliantly.

Marjay, what compressor bleed tool do you use? I have one and quite frankly, it's crap.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 11:35 - 12 Oct 2010    Post subject: Reply with quote
Joe wrote:
I recently did the reverse bleed method on a clutch (same principle) and it worked brilliantly.

Marjay, what compressor bleed tool do you use? I have one and quite frankly, it's crap.


Its a Sealey one which draws the fluid through into a bottle. It has a handle on it with a trigger.

Admittedly it was better until I used it on a car which has a large bleed nipple, and it ruined the rubber seal on the end, so it doesn't work as well for bikes now.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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Quote Me Happy



Joined: 15 Jan 2005
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PostPosted: 11:44 - 12 Oct 2010    Post subject: Reply with quote
I'm pretty sure I have the sealey one but I could never get a good seal on the bleed nipple. I can hear the air rushing past.
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sparkywilliam...
Scooby Slapper



Joined: 27 Jan 2010
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PostPosted: 15:18 - 12 Oct 2010    Post subject: Reply with quote
Marjay is it like this:
https://www.diytools.co.uk/diy/Main/sp-2-11813-94638-sealey-vacuum-tester-%26-brake-bleeding-kit.asp
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neil.
World Chat Champion



Joined: 24 Feb 2008
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PostPosted: 06:38 - 13 Oct 2010    Post subject: Reply with quote
Take the caliper off and get a g-clamp on it so the piston is held right in the bore, but not too tightly that you damage stuff. Just enough to stop air bubbles forming behind it as much as possible. Then be patient as it takes a while but you'll know when it's done because there will be no more bubbles in the fluid coming out of the tube and the lever will feel a bit firmer/stiffer as you squeeze fluid out by itself. I never bothered with reverse bleeding or vaccum kits with mine, just a piece of hose and a jar. It just took a lot of patience, but wasn't really difficult. Keep the master cylinder open and topped up whilst you do this and keep the brake fluid away from anything painted as it'll strip the paint. Wrap an old sock around the master cylinder.
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CBT February 2008 | A2 June 2008 | Yamaha YBR125 (written off) | Honda CBF125 (current)
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