Hello, I have a 1994 Polaris 300 2x4 and I found a set of calipers for my bike but I am having an issue bleeding the brakes. I started to get a bit of pressure at the handle so I cracked the bleeder screw and got fluid coming out. I took the top off the master cylinder to top up the fluid and now I don't get any pressure at the handle. I hear an air leak from the top of the master cylinder when squeezing the lever now and I can feel air leaking from the channel that runs in the top of the cover. When I squeeze the lever with the cover off fluid will shoot out the top of the master cylinder but it doesn't seem to be pushing down the line. I have tried using vice grips on the line a few inches from the master cylinder to build pressure but the doesn't work either. Any suggestions would be appreciated. Thanks.

 

Is the baffle that goes inside the master cylinder required or will it work without it? I'm assuming I should be able to build up pressure without the cover on the master cylinder, is that correct?

 

If you can't build up pressure in the master cylinder,more than likely the seals are leaking on the piston.The best way to prime the old ones is to remove the line and use your thumb over the opening to prime one up. If that doesn't help along with clamping off the rubber brake line,rebuild or replace.To rebuild one of these older ones costs more than just getting a new after market one from ebay or amazon. If a master cylinder has been primed you don't have to have the top on to have pressure or to bleed the lines.A mity vac is still a good way to save time on brake line bleeding also.

 

I tried priming it and got good pressure against my thumb. I noticed if I cover the holes at the bottom of the master cylinder with my thumb then I get really good lever feel and the brakes work. I'm starting to think I have a large air pocket in the master cylinder where the line is connected.

Will aftermarket master cylinders work where they are designed for a banjo bolt and this has a brake line that goes directly into the master cylinder?

 

Then have someone use a mity vac while you're pumping the lever. This may solve the problem on removing air pockets and help prime it up. You have to make sure on the master cylinder as I've heard the banjo type doesn't have the same thread size for the older screw in lines,but the one I listed said it would work.This other one for sure should work. Higher,but a lot cheaper than replacing it with an updated Polaris master cylinder.

 

Thank you for all the information.