1989 Big Boss 4x6 250 Brakes

[Canyon Doug]

Just got the machine from a neighbor. The 'transmission" caliper doesn't grab at all... Wondering if it can be re-built and how involved that might be... Special tools? Do the Harbor-freight style bleed-it-yourself pumps work on ATV's and older Big Boss in particular?

May have to go through the entire brake system, although my neighbor said he did change the pads in the past year and put new fluid in... he was unable to bleed much out by himself though. So the brakes for the wheels will need bleeding at a minimum, maybe the calipers re-built...

How do you know if the master cylinders are no good? Leakage out of them?

Are there after-market rebuilding kits available? Any favorite brands or places to get them? I know from automobile parts houses, that sometimes there are places you should avoid all together.

Best place for new parts/

Many thanks and advise if I posted incorrectly or in the wrong area. Newbie here...

Thanks, Canyon Doug

[Bruce!]

Welcome to the board!

[Goldplug]

Doug,

I just got done rebuilding an 1989 Big Boss 4x6 250 and had the same problem. The brakes came in a box and the fluid inside was like sludge. I also found that most of the bleed valve were trash. I did pull the master cylider apart and clean it. I did not replace any parts since it all looked OK. I started by removing the bleed valve and flushing clean fluid through the lines by pumping the brake. After it came out clean, I put the bleed valve back and used a suction style bleeder to remove the air. I never pulled the caliper apart, but I did grease the slides on the other calipers.

The brake now work well. If I found a cheap rebuild kit, I would most likely rebuild them, but the money was spend elsewhere on the ATV.

I would go through the entire brake system. Important to be able to stop.....

A bad master cylinder would leak or not pump fluid. Make sure the inside is clean, fill with clean fluid, open a bleed valve, and see if pumping moves fluid.