Posted: 12:06 am Dec 07 2006
Aha... I think I fixed it.
My solution? I did everything people said in this thread...at the same time.
Teflon tape for the nublette
Syringe on the caliper
Turkey baster on the master cylinder reservoir
Two C-clamps on the brake pistons
Screwed in the brake lever adjuster all the way in
With the adjuster screw all the way in, I was able to pump much more fluid through the system, which saved me time and bolt tigthening cycles, (but is too much for me to use while riding because the tip of the brake lever is all the way to the bark buster).
I found a technique that seemed to liberate bubbles in the reservoir that eluded me before. I would push on the syringe, and then pump the brake lever. Not bad -- then I stumbled upon an epiphany...
I was pumping away when I noticed something. No matter how much I pushed on the syringe (which would ooze micro-bubbles into the reservoir; and no matter how much I pumped on the brake lever or pushed the syringe, there would always be some micro bubbles coming out of one of the ends. Lots of micro bubbles.
It dawned on me that I maybe I didn't have air in my line, but air trapped in the terminal ends of the system. What I did was to start with an empty syringe and a full (and repeatedly re-filling) reservoir and pump the brake handle until nearly all of the fluid was out of the reservoir. This would begin to fill up the syringe. I would use the turkey baster to re-fill the reservoir and continue pumping. All the while the bleed screw was left full open with the syringed connected to it via a Home Depot tube. I went through several cycles when the micro bubbles stopped being expelled from the caliper end.
Heck. It was old fluid, so I dumped the syringe and filled it with new DOT 3. Then I slowly pushed the syringe to pump the fluid back up to the master cylinder reservoir (using the turkey baster to remove the excess). I found another technique that seemed to liberate even more micro bubbles from the master cylinder. I would push-pump-push-pump-push-pump little amounts of fluid back and forth. Kind of like a mini tug-of-war between fleas... only instead of pulling, I was pushing.
Nearly each time I pumped the brake lever, more micro bubbles trickled out the hole...
...until there were no more.
I tightened the bleed screw and undid the C-clamps on the caliber and bolted it all together. I was going to give it a test roll and brake in the garage when I remembered that the caliper piston was compressed and would likely need a few reservoirs full of DOT-3 fluid to extend. I was right. I pumped it up and after two or so re-fills, found that there was actually pressure building up (resistance in the lever).
I buttoned up the reservoir lid again and pushed the bike down the driveway and slammed the front brake. It squealed to a stop.
I then started up the bike and ran it down the road testing the brakes. It was nice to see my front forks compress under the braking load. Something I had seen with the squishy KDX forks, but had not experienced with the new KX forks. On my last run I grabbed a handful of front brake and felt the rear wheel lift off the ground (my first near-stoppee).
My work here is done.
Rick
My solution? I did everything people said in this thread...at the same time.
Teflon tape for the nublette
Syringe on the caliper
Turkey baster on the master cylinder reservoir
Two C-clamps on the brake pistons
Screwed in the brake lever adjuster all the way in
With the adjuster screw all the way in, I was able to pump much more fluid through the system, which saved me time and bolt tigthening cycles, (but is too much for me to use while riding because the tip of the brake lever is all the way to the bark buster).
I found a technique that seemed to liberate bubbles in the reservoir that eluded me before. I would push on the syringe, and then pump the brake lever. Not bad -- then I stumbled upon an epiphany...
I was pumping away when I noticed something. No matter how much I pushed on the syringe (which would ooze micro-bubbles into the reservoir; and no matter how much I pumped on the brake lever or pushed the syringe, there would always be some micro bubbles coming out of one of the ends. Lots of micro bubbles.
It dawned on me that I maybe I didn't have air in my line, but air trapped in the terminal ends of the system. What I did was to start with an empty syringe and a full (and repeatedly re-filling) reservoir and pump the brake handle until nearly all of the fluid was out of the reservoir. This would begin to fill up the syringe. I would use the turkey baster to re-fill the reservoir and continue pumping. All the while the bleed screw was left full open with the syringed connected to it via a Home Depot tube. I went through several cycles when the micro bubbles stopped being expelled from the caliper end.
Heck. It was old fluid, so I dumped the syringe and filled it with new DOT 3. Then I slowly pushed the syringe to pump the fluid back up to the master cylinder reservoir (using the turkey baster to remove the excess). I found another technique that seemed to liberate even more micro bubbles from the master cylinder. I would push-pump-push-pump-push-pump little amounts of fluid back and forth. Kind of like a mini tug-of-war between fleas... only instead of pulling, I was pushing.
Nearly each time I pumped the brake lever, more micro bubbles trickled out the hole...
...until there were no more.
I tightened the bleed screw and undid the C-clamps on the caliber and bolted it all together. I was going to give it a test roll and brake in the garage when I remembered that the caliper piston was compressed and would likely need a few reservoirs full of DOT-3 fluid to extend. I was right. I pumped it up and after two or so re-fills, found that there was actually pressure building up (resistance in the lever).
I buttoned up the reservoir lid again and pushed the bike down the driveway and slammed the front brake. It squealed to a stop.
I then started up the bike and ran it down the road testing the brakes. It was nice to see my front forks compress under the braking load. Something I had seen with the squishy KDX forks, but had not experienced with the new KX forks. On my last run I grabbed a handful of front brake and felt the rear wheel lift off the ground (my first near-stoppee).
My work here is done.
Rick