Fort Worth Motorcycle Riders

Not sure what happened. Tried to use it and nothing. Pushes all the way down with no resistance. Gonna try and bleed the system first, but I think the cylinder is bad. No pressure at all. And yes there is fluid in the reservoir and lines... Thinking that or that the lines are plugged, but I would think I would get resistance then.

This may be an obvious one, but did you recently remove the rear wheel?

Nope. All the springs seem to be working fine and the rod actuates...

When you open the bleeder and push it does any air or fluid come out?

Open the cap and see if fluid is moving down as your stroke the pedlle. If it is, you have a leak/ air in the line. If you just see stirring in the fluid with no level drop, the master cylinder is bad.

Even a small amount of air will cause nearly no resistance in the peddle. Brakes move very little fluid volume, so the airs ability to compress greatly exceeds the volume moved to compress the fluid.

Open the cap and see if fluid is moving down as your stroke the pedlle. If it is, you have a leak/ air in the line. If you just see stirring in the fluid with no level drop, the master cylinder is bad.

Even a small amount of air will cause nearly no resistance in the peddle. Brakes move very little fluid volume, so the airs ability to compress greatly exceeds the volume moved to compress the fluid.

Well, installed the rear master cylinder rebuild kit and the rear stainless line (I know it's not needed in the rear) and everything is working great again. Bought the front stainless lines too so they are next on the list of things to do. Rode it to work today and the rear brake feels much nicer now.

Awesome!

Just got the front Galfer lines installed. Bleeding a completely empty brake system sucks balls...

Speed bleeders are your friend. So is a decent MityVac setup.

Otherwise, its only about 150,000 manual strokes until you reestablish the vacuum.

Yeah...added speed bleeders too. I actually removed the bleeder completely and pumped until some fluid came out of the hole. Then I re-installed the bleeder. Did that on both sides twice before I started getting some fluid moving nicely.

Another option is gravity bleeding to start it off. Just pop the master cylinder cap and open the bleed valves then just let nature do its work. This allows you to bleed both sides at the same time but it does take a little while. Plus once you get fluid you need to reinstall the speed bleeders and use them to be sure you have no air.

I actually think the speed bleeders weren't opening much due to the lack of pressure in the system. Taking them completely out got everything started. Then I held the lever once they were re-installed and the lines started burping air bubbles...

Feel is better with the new lines. I think better pads would help even more without going the full monty and buying a Brembo master cylinder.

carbon fiber or bust

Make sure that you get ALL of the air out of the system. Sometimes air bubbles will hide deep within the lines and will eventually work their way up into the master cylinder. When that happens, you may suddenly find yourself without proper brake pressure, and Murphy usually times this to occur at the most inopportune of times. To prevent that from happening, make sure to bleed not just the valves by the calipers, but also the master cylinder as well. Start with the master cylinder, then the caliper that is furthest from the master cylinder, and finally the nearest caliper. Finally, zip tie the brake lever into the "braking" position and leave it sitting overnight. This will cause any remaining air in the system to travel up to the master cylinder. The next day, bleed the master cylinder valve one more time, and you're done.

Also, make sure that you do not overfill the brake fluid reservoir. Doing so will put pressure on the caliper pistons, which will cause brake drag.

Striple wrote:Make sure that you get ALL of the air out of the system. Sometimes air bubbles will hide deep within the lines and will eventually work their way up into the master cylinder. When that happens, you may suddenly find yourself without proper brake pressure, and Murphy usually times this to occur at the most inopportune of times. To prevent that from happening, make sure to bleed not just the valves by the calipers, but also the master cylinder as well. Start with the master cylinder, then the caliper that is furthest from the master cylinder, and finally the nearest caliper. Finally, zip tie the brake lever into the "braking" position and leave it sitting overnight. This will cause any remaining air in the system to travel up to the master cylinder. The next day, bleed the master cylinder valve one more time, and you're done.

Also, make sure that you do not overfill the brake fluid reservoir. Doing so will put pressure on the caliper pistons, which will cause brake drag.

So much of this smacks of "lessons learned the hard way". Good advice.

Yep, had one of those episodes happen during race practice Sunday morning at Cresson. Came flying into Little Bend (and later Rattlesnake), and suddenly found myself without brakes. Lever pulled all the way to the bar without producing any notable brake pressure. Rode it out by using engine braking and tipping into the turn to convert it into corner speed, which pushed me out wide, but at least it kept me from running off. Turns out there was a small amount of air in the master cylinder (which had just recently been bled) that cause it. No zesty when you're going into a heavy braking zone at triple digits...

Yikes!

What's the best way to bleed the master cylinder?

Same as the calipers.

My stock SV master doesn't have a bleed screw as far as I know.

You have a couple ways to do it. You can bleed all the fluid through the calipers and keep replacing the fluid till it all looks good and clean. It works but isn't perfect. You can get a vac system for cheap that is much better. You simply suck the fluid out of the master then replace it then bleed the caliper till all the fluid in the line is fresh.... much better in my opinion but the first method works if needed.