I have a 1985 Honda FourTrax 250. I just got a rebuild kit for the master cylinder on the front brake. There are no leaks anywhere and the pistons (I guess that's what you would call them) that push the brake pads out are working fine. BUT, you have to pump like crazy to even get them to catch. I've tried bleeding the lines but that does nothing. After pumping numerous times to get it to grab, IF you let the lever ALL the way back out the fluid rushes back into the reservoir. However, if you do NOT let the lever all the way back out you still have brake for 85% travel of the lever. Any ideas why the fluid might be leaking back?? I really don't see how it could be getting past that seal, it's nice and tight and brand new!!

Thanks,
Tyler

 

It sounds to me like you have air in the master cylinder. You need to remove the brake line from the master cylinder, then use a piece of rubber hose to insert back into the fluid thats in the master cylinder and then pump the lever until all the air bubbles are gone. You must leave the lid off to do this. This is a similar procedure to bleeding a car master cylinder. The only problem you may encounter is not having the right fitting to fit into the master cylinder to attach the hose to. In my case I already owned a mighty vac vaccum pump. I simply used one of the cone shapped plastic attachments and one of hoses from the kit to bleed my ATV brake system. You can buy it from a auto parts store for about $25 I bought mine at Auto Zone. After your done reconnect the brake line then bleed the wheel cylinders. Pump up the lever, then loosen the bleeder valve at each wheel (one wheel at a time) Then you should have brakes. One last point. Don't release brake lever until you tighten the bleeder valve at each wheel or you will draw air back into the system. Good luck!

 

I agree.....sounds like air in their somehow.

 

The easiest way to bleed the brakes is the same for a car.Pump(squeeze) your brake levers until tight.Then break loose the bleeder screw.DO NOT let go of the brake lever.It should want to move toward handlebars as the fluid runs from bleeder screw.Tighten up bleeder screw and then let go of brake lever.Do not let brake lever go before the bleeder screw is tight as this will let air in and youll have to start again.Repeat the process as often as it takes.DO NOT let the brake cylinder reservoir go anywhere near dry.Keep plenty of fluid in the reservoir.

 

Thanks for all the replies guys! ... Come to find out, air in the system wasn't the problem. And to tell you the truth I don't know that we actually fixed it but at least NOW we have brakes. My adjusters on the brake pads were rusted tight. After breaking them loose and cleaning it all up, we adjusted it JUST enough to where it was just skimming it. This SOMEHOW kept enough fluid in the system to where we have brakes even when we let the level all the way out. Just goes to show you when working on brakes you have to work on it as a system rather than look at individual parts! ;-)... Thanks again guys!