Brake and clutch questions

[Rupe]

Ok, my front brake feels a bit spongy and as the bike is an 02 I'm guessing the fluid has never been changed.

so while I'm at it I might as well change the front, rear and hydrolic clutch fluid. Can I use DOT4 brake fluid for all of these?

The way I was going to change the fluid for the brakes is to top up the fluid and keep releasing the bleed valve till clean fluid comes through. Then pump and hold the brakes followed by a quick open and shut of the bleed valve to get rid of any air. Does this sound right?

Not sure on the hydrolic clutch though, any help would be appreciated with this one?? Do I need to back bleed with a syringe for the clutch?

Also I have no idea how much fluid I need for all of this, any ideas?

[xwhatsit]

I don't think that technique will quite work. In my situation, at least, if you open the bleed valve, nothing comes out. You have to pump the brake lever for anything to come out.

First just pump the fluid out, but don't let it get so low it sucks air into the system.

Then the important bit is to get the air out of the system. What I did, was to get a spanner on the bleed valve so I could open and shut it (properly, no leaks) with one hand. Then what I did was put some pressure on the brake lever with one hand, and keeping the pressure on, open the valve. Before I ran out of travel with the lever (hitting the grip), shut the bleed valve tight. Then you can release the lever, and it'll suck some of the fluid back into the lines from the reservoir. If you do it right, any time the bleed valve is open there should be pressure on the lever. Keep doing this multiple times -- I did it from the `Upper' line to below the `Lower' line, and by that time my lever was nice and firm.

Make sure you don't suck all of the fluid out of the reservoir of course, otherwise you have to start from scratch.

DOT4 should be fine I would assume, DOT3 and 4 are compatible in the same systems together, but 4 is a bit better spec. I doubt you come into brake fade/boiling brake fluid very often in an offroad situation, you don't really need to brake heavily for sustained periods, do you? So the DOT3/4 comparison isn't too important. Even less so for your clutch.

[cheese]

Hey use teh 5.1 fluid. its much better. one bottle should see you right. You can buy a bleader kit from supercheap for about $20 I think.

[FROSTY:Me]

Dude thats how you DONT bleed brakes.
Fit a M8 ring spanner on the bleed nipple.Fit a piece of clear tubing over the nipple bit of the bleed nipple.Run the other end of the tubing into a jar with clean brake fluid in it.
Remove the topof the master cylinder .Squeeze the brake lever and crack open the bleed nipple. Tighten the bleed nipple and pump the brake lever untill it goes hard again --repeat until the brakes are hard.
In the situation of planning to fully change the fluid. I would use a syringe to remove the old fluid from the master cylinder then replace it with new stuff -saves a bit of time

[barty5]

stick bike on trailer bring my workshop and use air bleeder to do it should take you longer to put bike on the trailer than doin the job but it will be done well with no air in the lines

[xwhatsit]

Dude thats how you DONT bleed brakes.
Fit a M8 ring spanner on the bleed nipple.Fit a piece of clear tubing over the nipple bit of the bleed nipple.Run the other end of the tubing into a jar with clean brake fluid in it.
Remove the topof the master cylinder .Squeeze the brake lever and crack open the bleed nipple. Tighten the bleed nipple and pump the brake lever untill it goes hard again --repeat until the brakes are hard.
In the situation of planning to fully change the fluid. I would use a syringe to remove the old fluid from the master cylinder then replace it with new stuff -saves a bit of time

Isn't that basically the same method I described? Or were you referring to his original post

DOT 5.1 I think you should be wary of. Isn't it designed for newer lines, and doesn't work well with standard-style lines? Or is it vice-versa (don't use DOT3/4 in DOT5.1 lines)?

[rijekaz]

Fit a M8 ring spanner on the bleed nipple.Fit a piece of clear tubing over the nipple bit of the bleed nipple.Run the other end of the tubing into a jar with clean brake fluid in it.
Remove the topof the master cylinder .Squeeze the brake lever and crack open the bleed nipple. Tighten the bleed nipple and pump the brake lever untill it goes hard again --repeat until the brakes are hard.

That's the method I've always used and it's never failed.

[GR81]

sounds like you were both describing the same thing lol

[Danger]

5.1 fluid is fine and has a higher boiling point which helps in the rear system. Its 5.0 fluid that you should not use and is not compatible.
Before attempting to bleed your brakes try placing your knee against your caliper and holding the wheel in your two hands press your knee into the caliper which will push the brake pads back into the caliper and if there is an air bubble near the top of the line it will force it back into the resorvair. Then try your lever and see if it has firmed up (it will need pumping to extend the pads to the disc again). Of course your brakes should still be bled as the old fluid will have absorbed moisture over this time and will need a freshen up, but this will get you of to a good start.

Don't use brake fluid in your clutch, it uses mineral oil (in the KTM's at least) but I have never had the need to replace the oil in my hydraulic clutch.

[FROSTY:Me]

Not getting into a pissing match here but by NOT running a line into a bottle/jar with fluid in it A) you blow a nasty fluid all over the place as you squeeze the lever--Brake fluid is VERY bad to get on paint n stuff and B)Yo potentiially suck air back into the system which goes against what you are trying to acheive.
RE Mineral oil--Dude thats a new one by me --DO NOT assume what fluid it is cos if ya get it wrong theres a bunch of quite expensive seals will be buggered
Look at what it says on your clutch master cylinder

[Coldrider]

for $15 at Supercheap autos you can buy a bleeder kit, a tube with a one way valve on the end. When you have changed the fluid, dip the valve end into a container, the tube end on the bleeder nipple, and pump the lever till no air comes out of the tube, snap nipple closed, remove tube off nipple. Clean, easy and a one man job.

[xwhatsit]

Yes, mineral oil in the clutch lines seems funny -- wouldn't it just compress?

Is there not a bit of confusion here between hydraulic clutches (like the one he's got) and the oil you put into the clutch?

[Danger]

If you have a hydraulic clutch check the resorvair lid. The KTM's use mineral oil not brake fluid. Check yours and see for yourself.

BTW, oil does not compress, ever!

[Rupe]

thanks for all the help guys.

The brake master cylinder says use DOT 3 or 4, and so does the clutch. So I guess that solves weather to use 5.0 or mineral oil etc.

Barty, thanks for the offer but I not getting back onto the shore till near 6pm at the moment so you'd probably be home by the time I got to the garage.

Probably get one of those kits from super cheap.

Still not 100% sure how I'm going to do the clutch though as you can't pump the lever it till it gets hard.

[Reckless]

you'll be ok mate.
Easy as you can see the bubbles coming out though the clear tube.
Main thing to remember is do not release the lever till you have the nipple closed again weather or not you have pressure. Once you have pressure and the lever doesn't go to the grip when you pump it up, you will be able to feel it go down(push the fliud through) when you open the nipple, just hold it against the grip till you have closed the nipple again. Its the letting it out of the lever when the nipple is open that sucks the air back up the plastic tube and into the cylinder.
You will have to, pump up, open nipple, close nipple, pump up etc a few times till you see no air being pushed though the clear tube b4 the job is
done.
And don't forget to continually observe the master cyl fill bowl. If you let it empty and get air in from the top you will have to chase that all the way down the brakeline till it comes out of the nipple. Refilling this comes after close off of nipple and b4 the next pump up routine.


Once you get the hang of it its easy and a good thing to teach yourself as it should be part of your maintenance..

Other common factors on poor MX brakes apart fronm worn pads are

"discs need a clean", thinnners or brake clean them. As the washing soap and detergents get on them.

Caliper halfs do not move freely. Most MX Pistons only push from one side so the far side usually gets pulled towards the piston when the brakes are appied. On mx bikes there is so much dirt around often the pins the halves slide on get gummed up!