Bleedin brakes
 

Went to track day. Progressively lever lost feel and finally pulled back to bar.
Bled brakes with me mityvac. Went fine but no change. Bloke came along and seemed to open the bleed nipple very slightly, pull back the lever, close the nipple. He repeated this about 20 times. Result rock hard brake lever for rest of day.
Can anyone confirm what he was doing and why it made the difference it did?
I did not watch closely enough...git. :rodent:

That's normal for bleeding brakes innit? Except I've only ever seen it done that way when no tube was available and we needed to get my mate off the motorway.

Yup, done this myself a few times. I usually use the vacuum pump method as well, but every once in a while the last bit of air won't come out, and then pushing out the air with the lever seems to work well, especially at the master cylinder. Just make you ALWAYS close the nipple before releasing the lever.

That's why I fitted speedbleeders to mine, instead of buying a mityvac.

Process is basically

squeeze lever
open bleed nipple slightly
When lever runs out of travel, close nipple
release lever

repeat until done, then swap sides. Using a piece of clear hose lets you see if there's any air bubbles coming out, and keeps the area clean of fluid.

Strangely enough, I've just bled mine with 5.1 this morning. Had a problem on a trackday with the reservoir hose kinking and not allowing the M/C to fill, so got progressively more lever travel until it was spotted. Hose is now braced...

Cheers. Felt like a muppet for asking really. As usual however answers are informative and helpful. ;)

Very normal way to bleed brakes. I only use a pump when I'm doing something major like swapping the calipers out or installing new lines or something. I always finish with manual bleeding as you describe. You can also get the last little bit of air out by putting a zip tie squeezing the lever overnight. Just run it around the lever and the grip and pull it until it's firm (but not so tight that it gouges the grip or anything). In the morning, do one last squeeze/loosen/tighten/release.

Yep thats the way to bleed with no hose/anti return valve.

Yes the best way without doubt, just time consuming.

Ha! Having bled my back brake with my mityvac this afternoon, and got it rock-solid, thought I'd try this short-cut method on the front, which wasn't *quite* as good as it could be.

Little bit more, little bit more.....


Soddit! Got air in the bloody thing: lever coming right back to the handlebar with no resistance whatsoever. :mad:


Oh well. Thought this meant I'd better do the damn job properly. So off with fairing and nose-cone. Not essential, I know, but I prefer it cos it makes access to the reservoir cap and the master cylinder bleed nipple a breeze. The master cylinder bleed nipple in particular I always find a right pig; the throttle cable always gets in the way.

I bled and bled and bled, and now it's better than ever. :bouncy:
I think part of the trouble is the bleed nipple's a bit worn; the hexagons are rounding off a bit, making it difficult to tighten. I'm sticking to using a ring spanner in future.
Must remember I'll get a new nipple fitted at the next service.

[Edited on 25-6-2005 by moto748]

Just get these

http://www.speedbleeder.com/

I swear by them.

got the bleedin procedure down to a fine art. Next thing is how to find out where the system is losing pressure / lever going soft.

Any ideas or experiences. Is it a dealer job? :mad:

Have you changed any lines recently?
Used new copper washers if you have?
Are you losing fluid level in the master or is it just "going soft".

Any leaks will be apparent at the washer joints cos it's under pressure.
If it's going soft cos of air, then is your master level staying high enough when the lever operates and is your master upright or have you put it at an angle on new bars?
Check yer nipples

What fluid are you using? Could be that you are using your brakes so hard that you're boiling the fluid, but this is unlikely.

More likely explanation, assuming that you've got braided lines, no fluid leaks, good piston seals and blah blah blah is that the brake fluid that you used might not be as fresh as it could be. Brake fluid is hygroscopic and quickly absorbs moisture from the air unless it's in a sealed container (or a sealed braking system). If your brake fluid gets contaminated like this, the water content that's now part of the brake fluid will boil off leaving you with a spongy brake lever (cos now your brake fluid contains a gas that can be compressed instead of a fluid which can't be)

To try and locate a leak, dust the joints down lightly with talc, apply a little pressure to the lever (tie wrap or similar) then leave overnight.

If there's a slight leak the fluid will the forced out and caught by the talc, this makes it a lot easier to see as it'll appear as a clumped mass (you can do the same for oil leaks)

Also, check the reservoir and hose, if it's kinked or blocked it'll give the impression that you're losing the lever because the M/cyl can't be refilled to compensate for the pad wear ( had this at Cadwell, it's disturbing!)

If it's not leaking and the lever's fine, swap fluid type to 5.1, it should be a lot harder to boil the fluid then, and if I remember rightly it's less hydroscopic than 4.