brake reassembly

[mixelpix]

hey all,

I flushed the system and tried poking around the master cylinder with some really thin wire and everything seems clean, but my brakes don't want to release now that I've reassembled everything.

from a complete reassembly, how far in should I seat the piston prior to adding fluid? does it make a diff?

thanks!

-pdk

[prometheus578]

Did you take apart the master and both brake calipers? Was it just a"2 year" maintenance fluid change, or was there some problem initially? Caliper pistons should be able to retract fully into the caliper. Do you have play in the brake lever... I mean.. when you squeeze it, does it return under spring power? Front or rear brakes? Is the caliper on correctly?

, how far in should I seat the piston prior to adding fluid?

We're talkin brake caliper piston, yes?

[mixelpix]

hey Prometheus,

Sorry I should explain a little more. My '79SF was in a front end collision almost a year ago. I was able to ride her home at the time, but the front right stanchion was visibly bent (slightly) and something up front was scraping and rubbing against something the whole way home - it turned out to be the fender if I recall. The collision was a total t-bone - the impact was on his driver side (he made a sudden U-turn w/o signaling and then stopped in the middle of the road). When we hit, my bike's handles turned left and the right side of my fairing and forks took the brunt of the impact. The pacifigo fairing was left with the driver's sideview mirror inside a big hole. I think I was going around 25-30mph, slammed on the brakes and jumped up for the hit ...did a nice roll over the guys hood, too (after snapping my windshield in two.) Police report states - with 2 witnesses - it was his fault. 'Course he has no money -or- insurance... I flew to Oregon to buy this bike. Engine had even compression, a full bagger, under 30k - rode it like a dream almost 1,000 miles home - even got her up to 105mph - and a month later Leroy Washington decided it was time to take it off the road. thank$ Leroy.

As I've been doing the removal and installation over the course of available weekends with available parts from eBay, I've replaced the forks, trees and now the left rotor. In addition to mutzing up the throttle stop screw, the throttle linkage (on the carb side) and the carb/air filter assembly, the impact also seemed to have warped the front left rotor. After reassembling everything when I got the forks/trees replaced the front right rotor was flush against the inner side of the pathhway through the fork. It's now been replaced. The right rotor is still original and at this point all seemed to fit well. I removed the left caliper to replace the left rotor in situ but then I had a byatch of a time getting the left caliper back on. It had been sitting for a while by now. I took it apart and cleaned out the obvious gunk, but there was nothing overtly wrong. I compressed the caliper piston all the way back in and reassembled the caliper, and fit it to the leg with a little wiggle room. When I re-installed it I also flushed the fluids and I thought I felt the piston pop out when I was bleeding the line. I haven't messed with the front right brake/rotor except to swap out rotors. Still the original wheel too.

So, this is my first time working with brakes and I am sure there is something basic I should be considering, or reconsidering. It seems like the pressure is either holding the pads against the wheel and won't release, or there is something stuck. Either way I should probably take both front calipers apart completely and replace the consumables. The Master cylinder isn't the cleanest it could be either, but I poked around like recommended in the maintenance section. There isn't any gunk in the line, the hoses don't give under pressure and the fluid was only a light brown when I first inspected it...

Any thoughts or advice would be greatly appreciated!

Thanks,
-pdk

[mixelpix]

Originally posted by prometheus578
Do you have play in the brake lever... I mean.. when you squeeze it, does it return under spring power?

yep, it feels like normal brake action.

when I put my hand around the different brake lines on the front brake system, none of them feel like they are expanding from pressure, I've tapped the heck out of all the banjoes trying to eliminate air, left it sitting overnight with the lever compressed...

I have a very well kept LG which I have been comparing against. on the LG, when I compress the lever with one hand and feel the right or left brake pads with the other, there is a slight wiggle. Also, the front wheel rotates freely. On the SF, I get no wiggle and the wheel won't turn from the pressure on the pads.

Thanks!

-pdk

[prometheus578]

"The wheel in the sky keeps on turnin'"

HHmmm somethin' not right here. All things being equal, when the brake is applied, one would expect to be able to feel the caliper twitch a little. Two things: there is air in the lines, and not enough force is being applied to the caliper to, after the pads make contact, cause it to twitch. Secondly, the caliper doesn't twitch 'cause it's deployed against the pad as far as it should, but it's not rebounding back to it's starting point. Or the caliper is binding somehow with the rotor.
Do you follow me? (Well quit following me or I'll call the police:Groucho Marx) I'm not a Special Guy (Oh, I'm Special, all right), but isn't there some odd proceedure when putting the tire back on.... something about spacing the rotors in the forks? can't recall. What about the wheel. No damage there from the impact? Take the calipers off, and raise the front end of the bike. Spin the wheel... no probs? Now, turn the wheel all the way to one side. Take a can of something, carb cleaner, whatever, with a straw nozzle. Set the can next to the tire, with the nozzle against the rim. Slowely spin the tire, watching the nozzle. If the rim's out of whack, you should see the space between the straw and the rim increase, then decrease as the tire is turned. a certain amout of "runout" is ok, but really loopy is something else. Good, now do the same with each brake rotor. The brake rotors might be good, but the area of the rim they attach to might have been honked by the crash. If this is loopy, could cause the calipers to bind.

[mixelpix]

thanks for the tip on the tire check - yeah, there prolly is some "Special" procedure. I'll keep diggin through the archives when it's too cold in the garage to work anymore...

[DiverRay]

mixelpix,
I have a "spare" good front rime from a '79 standard. I'm not that far away, but don't have a running car at the moment. If you need the rim, let me know. If you can get down to Aptos, it's yours.
Ray