sportsman 500 1999

[luckyhook]

My master cylinder on handlebar keeps pressurizing and locking my brakes up. I then let fluid out and it is ok for awhile but then prressure builds up again and handle and brakes are locked up again. what should I check to be the problem. Could it be the master cylinder itself or a different part of the braking system?

[pjmartin]

There is a compensation port at the bottom of the reservoir and a vent port above the diaphragm. If these are blocked the fluid can't come back into the reservoir when the lever is released.

[Bruce!]

Welcome to the board!

[luckyhook]

Thanks for advice, checked the ports and they seem to be free. I am ordering a new mastwrcylinder, hopefully that will clear it up.

[tt425]

I agree with pjmartin. Vent stopped up on the master cylinder cover. Make sure to use good clean brake fluid. Over a short period of time brake fluid draws moisture. Water in brake fluid will cause a problem. If brake fluid is dirty drain what you can by loosening lines or bleeder screws. Starting with the right front brake,try bleeding the brakes. They brakes are sometimes hard to bleed. If you have trouble bleeding them try this with the master cylinder empty ans the cover off: Use a squirt oil can(Metal hand held pump oil can) with a metal spout and a piece of hose on it. Barely loosen the bleeder screw, attach hose and start pumping. This will fill the master cylinder and you will be able to bleed the brakes easier. I hope you find the cause of your problem.