Observed Trials

Hey, All!!!

I hate to continue to come on here with pleas for help. But I am having a heckuva time trying to get some back brakes on my 2010 280 Gas Gas, & wonder if any of y'all have ever had to beat this deal, & how you did it.

This isn't my first rodeo with bleeding brakes. My KTM's front could be a booger to get air-free at times, but was still pretty easy compared to the rear brake on this Gas Gas.

I recently had the swingarm off the bike, cleaning/greasing/replacing swingarm pivot & linkage bearings & seals. Since the brake line runs through the swingarm, and I thought I needed to remove the swingarm, I disco-ed the rear brake line. Got everything back together. New bearings & seals in the dog bones & linkage, new grease & seals for the swing arm. Have new crush washers on each end of the brake line, and seem to have no leaks.

I backed off the pedal adjustment rod into the master cylinder, to be certain the piston in the m/c could return & uncover that port in the m/c bore.

I've tried loosening the banjo bolt(s) & pushing down on the pedal, in an effort to possibly get any air out of the master cyl. & caliper. I've used a syringe to force fluid through the system from the line for the reservoir back to the bleed nipple, like in Jim Snell's video at www.trialspartsusa.com . I've tried bleeding with the syringe hooked up to the bleed nipple, and forced fluid backwards up into the reservoir. And I've bled the goofy thing "conventionally", by pumping the brake pedal & holding it, while cracking open the bleed nipple & closing it before allowing the pedal to return back. And I've still got really, crummy brakes in the back. I've gone through a whole quart of DOT 4 brake fluid, almost, and still have funky brakes.

Actually, the pedal feels fairly firm after all this. It just doesn't seem to force the pistons out of the caliper far enough to really clamp down on the rotor. My "benchmark" of how well the back brake is working is by standing on the bike in my barn, balanced, and then do a front wheel hop. I figure if it clamps hard enough for me to hop the front wheel on my concrete floor, as it used to do, it's likely as good as it ever was. Or, if the rear wheel skids on the concrete, instead of rolls, I'd think my brake is OK. Every now & then, it does seem to hold well enough to hop the front wheel, but it taks a lot of pedal pressure. Most times, the wheel "spins" while the brake makes a kind of moaning/squawking sound as I go backwards a few inches. I'm now currently waiting for new brake pads, and will try those. Maybe I got brake fluid all over the old pads? I know this has been one of the messiest deals I've ever had doing this job. The old pads still have about .100", or 2.5 mm of material left; I'd think that would still be in allowable limits.

I still have my fuel tank off, my airbox/rear fender off, & even my muffler off (waiting on O-rings & a new crush gasket for the exhaust) while I work on the bike. One positive about all this is that the bike seems INCREDIBLY easy to balance without all that stuff on, for some reason....

Anyway, sorry for the novel here. I'm hoping that with all this info, someone can maybe think of something else I need to try, or tell me what I've done wrong, or??

Thanks for any advice, cussing, help, or hand grenades you may be able to lend!
Jimmie

Well, I *think* I have it now.   :-\

For the second time, I let the bike hang with the rear wheel up in the air again overnight. Tapped on the m/c & caliper with a wrench for awhile, in an effort to dislodge any air trapped in there, and bled it again today, conventionally. Has a nice firm feeling at the pedal now, but still doesn't stop as well as I'd hoped it would....   ???

I'll put my new pads on when I get them in the next day or so, and will try the "heat-the-disc-up-by-dragging-the-brakes-and-then-douse-it-with-water" trick per Ken Levens' instructions. That guy has been a metric ton of help to me. Thanks, Ken!

I'm also waiting on an exhaust gasket (the one at the cylinder), so won't be able to ride the bike to try the water deal for a bit longer. Will report back on how it goes then.....  ::)

Best Fishes,
Jimmie

I have a couple of crush gaskets for the head pipe if you need one let me know. If the mid-Pipe ones look ok clean everything up reel good and use high temp silicone on the mid pipe when putting it back together. I like to let it set up overnight before I start the bike if I can.
  Also make sure you have a little bit of play in the rear brake pedal. If the piston can't go back to center you will never get the air out of the system. This goes for the clutch as well. This will also stop any problems once the system gets hot due do expansion.

Thank you, Brian!!!

Brian, would you possibly happen to be the guy that Ken L. texted a question to on my behalf? He said "Brian is a really good mechanic; I'll text him a question for ya."

I did indeed make certain that I had plenty of "slop" in the brake pedal before attempting to bleed everything. I adjusted the threaded rod that goes from the brake pedal up into the master cylinder. I had read the numerous warnings on the web about this, as well as actually been bitten by it on my old KTM years ago....  :o

The pedal now actually "feels" pretty good, but my back brake does not work for squat. I rode around just a little tonight, after I borrowed an exhaust gasket from Kenny, and put the bike back together. I didn't get to ride enough to get the brakes hot to do the "water trick", as I made a mistake when I put the bike back together, and had an intake leak where the airbox snorkel clamps onto the carb. That little rubber spacer/"adaptor" on the end of the carb had gotten "pushed" back into the airbox snorkel when I put the airbox/fender back on, & it was dark before I figured out what was going on & fixed it.....

So, I really need to get this figured out by Sat., if possible. Will there be any long, steep downhills for the Novices at Dallesport, either in sections or the transfer trails between sections? I'd really like to ride that event Sunday..... I have new Gas Gas/Galfer brake pads, and am wondering if I should try them?

Jimmie