79 Special Brake Problems

[egsols]

Own 79 special. just rebuilt front master, new seals on front calipers and installed russell braided lines. Trying to bleed system and can't seem to get air out of right side caliper. Pulled caliper noticed small scratches on piston. Replaced piston with one from parts bike that looked good. Still can't get air out of right side. Read about tapping splitter which I'll try tonight. Read about bleeding MC but don't know how? Any ideas?

[Winterhawk]

Use a vacuum pump and pull the fluid through the bleed nipple.

[fredintoon]

What Winterhawk said - - -

- - - but before you start, seal the the bleed nipple thread with teflon thread tape. Or others have used dielectric grease as a thread sealant. This stops air being sucked into the system around the thread as the Mitymite or other vacuum pump sucks on the system. Or say "hang the expense" and swap in Speedbleeders.
http://speedbleeder.zoovy.com/category/features/

[fredintoon]

come to think about it, even Speedbleeders would need their thread sealed with teflon tape or grease to stop air entrainment once you crack them loose, right?

[fredintoon]

About that brake piston - - -

- - - it ain't that. The only thing that's important is the caliper bore, the seal ring groove and the seal itself. So long as the piston moves freely in the bore it's surface condition don't matter.

[EZMoney]

If you have all the air out from the master cylinder down to the left caliper then it is just a mater of time until you clear the right side. Make sure you don't run the fluid dry in the master and there is no choice for the air but to be forced out the bleader. You just have to be patient. I completely drained and rebuilt mine this spring and it does take a little time when you are doing it from the brake lever several pumps at a time. Remember to hold the lever compressed when you open the bleeder and don't release it until you have closed the bleeder.
My $0.02

[TopCatGr58]

Hey Ed,

Another technique is to take the caliper OFF the fork, get a box or something that you can put it on up above the height of the splitter, and put a piece of wood inbetween the brake pads the same or slightly thicker than the rotor, and then bleed it that way, so the bubbles are rising TO the caliper, instead of possibly rising back up in the brake line hose when it's above the caliper!
T.C.

Hey Fred, I'm not so sure about what you said regarding the piston conditon?! The O-ring fits into the caliper bore, not fixed to the piston, SO...the piston has to slide in and out past the caliper fixed square O-ring, and so IF the area that the piston is sliding in and out has pits/scratches deep enough, then it could damage the O-ring or leak, not seal adequately....at least that's the way I see it!
T.C.

[EZMoney]

You are right about that TC it would make it a little easier other than it is a pain as you have to unbolt everything and then hunt around for a piece of plywood or something to put between the caliper as to not push it out. I have been beeding brakes for years in cars and the master is alwasys above the wheel pistons. The air bubble will be forced down the line as long as you don't wait a long time to allow the bubble to work it's way up. The viscosity of the fluid over the air will move it along. It works every time as long as there are no leaks in the lines

[fredintoon]

seal groove placement

TC posts:-

Hey Fred, I'm not so sure about what you said regarding the piston condition?! The O-ring fits into the caliper bore, not fixed to the piston, SO...the piston has to slide in and out past the caliper fixed square O-ring, and so IF the area that the piston is sliding in and out has pits/scratches deep enough, then it could damage the O-ring or leak, not seal adequately....at least that's the way I see it!
T.C.

Hi TC,
Clymer's shows the Standard front caliper with the seal groove in the piston. Stupid bastards don't show the Special front caliper piston at all. Rockjok's CD has such a poor picture of the Special's caliper that one cannot see if the piston has a groove or not.
(And what with rebuilding both Special and Standard calipers over the years I don't remember which way round the Special's caliper is)
But I used to design o-ring & tetraseal installations and here's what I know:-
The seal is between the seal groove, the surface the seal slides against and the seal itself. The condition of the other surface, the one the seal don't slide on, don't matter. If the groove is in the piston, the piston surface don't matter. If the groove is in the caliper bore, the caliper bore surface don't matter.

[egsols]

Hi Fred,

The seal is in the caliper bore on my special. I pulled the caliper and checked for fluid on the piston, will I was moving the lever. Didn't see any. If it was sucking air between the seal and piston wouldn't it also leak fluid back?

I'll probably grab a pump cause I still can't get the air out, but I'll also try to bleed the MC by cracking the banjo. Is that how they are bled?

[fredintoon]

Banjo bleeding

Hi Egsols,
bleeding the M/C through it's banjo can work but it's kinda messy. Hang an ice cream pail on the bars to catch spilled brake fluid, that stuff is a dandy paint-stripper. If the caliper is empty of fluid after it's rebuild there could simply be too much air in there for the traditional open, squeeze, close, release, repeat bleed sequence to cope with. A vacuum pump should work OK though. Although I couldn't remember which way round the Special's calipers are, I do remember that bleeding them was no problem, especially compared to the hassle of bleeding out the dual disk conversion on my XS650 which took what seemed like forever. OTOH, my XS11 Special sat for weeks between when I refilled the system and when I bled the air out. Perhaps simply sitting there allowed most of the air in the system to just bubble up into the reservoir? Two things about the bleed nipples; 1) thread tape or grease the threads to stop air entrainment. 2) carefully check the sealing cone to make sure Mr Longwrench didn't overtighten the nipple enough to crush it out of shape so it will not seal.

[John]

Previous Tip

http://www.xs11.com/forum/showthread...676#post126676

[egsols]

Awesome tips,

I was thinking of just setting up a spare set of bars beside the bike to mount the MC, and bleed off the banjo from there so as not to get fluid all over the bike. I like the idea of turning the MC over and I'll let you know how it turns out.

[egsols]

Nothing has worked so far. I used the vaccuum pump, looked like all air was gone but first pull felt soft with next two or three pulls on lever nice and firm. The difference between the first pull and the following ones noticable.

I figure maybe the front right caliper was sucking air so I swapped in a single banjo at the splitter and rebled with just the left caliper. The lever became firm in no time. I then removed the left from the system, drained all fluid and retried with just the right side. Again I got a firm lever.

I then thought maybe the double banjo was the problem so I moved to the left caliper to avoid having it at the splitter. I then ran the right side line over the fender and rebled. Still getting a soft pull on the first try.

Any ideas?

Frustrated

[egsols]

Just an after thought, I noticed that the holes in the banjos I am using for the new russell lines are a lot smaller than the stock ones. Would that make any difference?