bleeding front brakes
 

hello everyone
I have a 1984 xt 600. I bought a new front master cylinder. I have tryed to bleed it like I would on a car, pump it up, hold it, crack the bleeder and tighten it back up, done this over and over but I am not getting any pressure built up.
Is their a trick or something I need to do different on a bike?
thank you

You need to open the bleeder then pump the lever fairly quickly(topping-up the fluid at the same time) until all the air is expelled from the bleeder, & then close the bleeder.
The way you were doing it was allowing the air to float/travel back up the hose after each time you closed the bleeder.
Being a new master cylinder you may have to bleed that first.
Bob

Hey all!

If I recon well, when I last did this same thing what I did was open the master cylinder, put oil in it, squeezed the brake lever a a lot of times and kept topping up the oil until very little air came out over the top of opened master cylinder.

Only then did I went for the squeeze squeeze squeeze squeeze and keep squeezed and loosen the banjo on the brake caliper just a wee bit for air to come out and retighten it by hand....

I repeated this untill it streamed out some highspeed jets of oil a couple of times and tightened and assembled everything back together....


It's a very easy thing to do I guess..

Vando :cool4:

The way its done is fill the master cylinder give a few pumps of the lever then open the bleed nipple pull the lever in slowly until it touches the bar hold it there and tighten the bleed nipple, repeat as needed. If you still have no luck after 5 minutes or so then acquire a syringe place a piece of tube on it and attach it to the bleed nipple draw the fluid through (dont forget to close the nipple if you have to push the syringe in) make sure you keep the fluid topped up. In the workshop we have a vacuum tool for the job but the syringe is cheaper and will do the same job (the bigger the syringe the better). Another tip is to push the pistons back in the calliper as this removes the space that air can fill.

I normally suck the fluid through from the reservoir through the caliper using a large syring & battery breather tube, you just need to keep an on the fluid level in the reservoir unless you want to experience the brake bleeding equivalent of Groundhog Day........ :rolleyes2:

Once bled, pump the lever a few times & cable tie (or similar) the lever back to the bar's and leave overnight. Any air trapped in the system will hopefull migrate to the highest point of the caliper i.e. the bleed nipple. Open the nipple, bleed the air & check fluid level again. I've sometimes sucked the fluid out of the reservoir with the syringe & pumped it back in to the caliper via the bleed nipple and up in to the nearly empty reservoir, taking any trapped air with the flow.

Don't push the pistons all the way back in to the caliper as there comes a point whereby there's not enough fluid behind the piston to move it (DAMHIK).

The best £40 you will EVER EVER spend.

Mityvac Brake Bleed Kit

http://www.dm.net/%7Ebahwolf/bb2004/brake-bleed.jpg

another brake bleeding tool as ted says if your going to bleed brakes regularly it will be the best money you spend but as a one off go for the syringe

Tools

I have one of those hand operated kits for sale if anyone's interested. No longer need it since getting a compressor.

I can't explain why this works, but it does. I've used it a few times on different bikes. Bleed as best you can using any or all of the above techniques then turn the bars so the master cylinder is as level as you can get it. Replace the cover loosely. Squeeze the brake lever and then hold it in with a zip tie or something similar. Leave it overnight and in the morning it should be fine as all the air gradually works its way up and escapes through the master cylinder.

reply
 

hello everyone and thanks for your replys.
I went to my local autozone and asked about a bleeder kit.
they sold me OEM/One man brake bleeder kit :

AutoZone.com | Brake Bleeder

came home and follow the directions and it worked perfectly I now have front brakes.
thank you everyone :)

Yes I heard that tip a few year ago after having major problems trying to bleed a front brake, for some reason its nowhere near as easy as bleeding car brakes, this thread should deter anybody from disconnecting their hydraulic brakes if they dont really have to and havent done it before/tried to do it before.

zip tie
 

My first post, awesome site guys. I just put hand guards on my 84 Xt600 and loosened up the brake hose to a downward angle instead of straight out to get the guard mount on. In just the split second i lost the bleed in the system.

zip ties, duct tape and wd40 work miracles.
I left my brake lever zip tied down over night came back this morning pumped it twice and was as solid as ever.:clap:

It desperately needs the brake fluid changed, only one problem.

my master cylinder cap is stuck, i cant get either screw to turn. At least not with hand force and a standard #2 screwdriver. I suppose i will try a tap or two on it with a impact wrench. worst come to worst i will drill out the old heads of the screws and hopefully be able to grab the remains with pliers.

You guys have already saved me a huge headache and ideas on getting the cap unstuck?

Drill the heads off.... I've had to do this with countless old bikes i've worked on. The bolts are M4 (I think) so use a 3mm or 4mm drill bit nice and slowly just to take the head off the bolt. It will leave about 5mm of thread which 99% of the time, will come out with grips with no effort.

Loads of places keep the bolts in stock. Even if you have to order them in, they're only a couple of quid. Those bolts are screwed anyway, so they need replacing.