Brake bleeding

[bosco659]

Doing an old virago for the neighbor. It barely made it to the garage, the front brake was sticking so bad.
View attachment 341126View attachment 341128View attachment 341130View attachment 341132View attachment 341133
It's getting SS lines. MIGHT anneal the old washers, but to be honest usually don't.
I removed calipers and pads with brake lines intact and forced out the pistons a ways with the master cylinder FIRST. THEN removed the lines etc. Took both hands on the lever to get all 4 moving, a flat bar in the caliper stopped one piston at the limit so the second would (reluctantly) pump outward.
Only one piston really fought me on the way out but cleaning, lubing with brake fluid, and pushing back in twice freed it up enough that air pressure popped it out. A bit of patience helps, the piston was moving VERY slowly with 80PSI applied but moving. I used a magic marker to gauge progress.
View attachment 341129
Note: I had a tapered drift blocking the rear port and a rubber head on the air gun nozzle to apply pressure. The passages are drilled at an angle into divots in the casting.

Those calipers look nasty. The ones on the XS looked ok but it required quite a bit of force to push the pistons in. 3 of 4 came out pretty easily with compressed air but the 4th was a bugger on both calipers. On my calipers, the halves can’t be separated but there’s a crossover line you can remove to isolate the the circuits. Once the easy ones were out, I removed all the seals. For the difficult one, I replaced the one piston (sans seals), held it in place with a clamp, then pressurized up to 175 psi (with a rag and aluminum block to prevent the piston from launching). It came out very, very slowly. At least this confirmed it was overdue for a refresh.

 

[ckahleer]

I replaced the one piston (sans seals), held it in place with a clamp, then pressurized up to 175 psi (with a rag and aluminum block to prevent the piston from launching). It came out very, very slowly.

does someone here know how much PSI is applied when hard braking?

 

[bazz]

For those of you who dont want to go through the annealing, this is where I get my copper washers from. I normally buy 50 or so of a few sizes to have on hand. I buy a Lot of the 6mm washers where weeping at a case bolt may be an issue
https://belmetric.com/washers/solid-copper-gaskets/

While you at it you can also pick up some gaskets for the oil and sump drain bolts
https://belmetric.com/washers/hollow-crush-gaskets/

These are stamped out
So should really be annealed before use

 

[Grimly]

Not an urban legend, something I have advocated and has worked for me over many years.

Yep, it's worked for me on a few occasions.
I also gave thought to never shaking the bottle of fluid, don't know how many times I've seen that done.

 

[cra-z1]

These are stamped out
So should really be annealed before use

I agree there is probably a slight degree of work hardening during the stamp process around the edges but not enough to compromise then rest of the sealing surface.

 

[bazz]

I agree there is probably a slight degree of work hardening during the stamp process around the edges but not enough to compromise then rest of the sealing surface.

Probably not
But for the sake of a couple of minutes work I always do it

 

[bosco659]

So, as posted elsewhere I discovered the hydraulic brake light switch on my master cylinder went belly up again - cheap Chinese part. I decided to get rid of the hydraulic switch and convert to a micro switch. I decided to remove the hydraulic switch fitting and replace it with a less bulky banjo bolt. I tried to do this with as little mess as possible, but ended up with brake fluid everywhere when I tried starting an M10-1.25 into the M10-1.00 hole. No damage done other than the mess I needed to clean up. Proper banjo ordered.
When refilling the master cylinder reservoir I used this tip to keep spillage to a minimum as well as minimize air intrusion into my brake fluid bottle. I can’t recall where I got the tip. If it was on this forum thanks.

 

[5twins]

So, brake fluid pours OK just out of those two little holes? I'll have to try that on my next bottle.

 

[bosco659]

So, brake fluid pours OK just out of those two little holes? I'll have to try that on my next bottle.

Yes the top hole acts as a vent. It’s a very controlled pour. Great for top ups. If you were filling a cars master cylinder it would be slow.

 

[bosco659]

I just saw a quick video on sealing pesky banjo bolts that continue to leak despite being tight. In the video, the guy tightened the bolt, then gave the head of the bolt a good tap with a hammer. This allowed about another 1/8 turn or more of the wrench and allegedly stopped the leak. The claim is that the tap “seats” the crush washer and doesn’t damage the threads on the bolt or caliper. Kind of makes sense because there’s play in the threads to begin with. When the bolt is tight and under tension, the threads are pulled tight against each other. A rap with the hammer moves the fastener and caliper threads “away” from each other. This is interesting and I’ll try it next time.

 

[Max Midnight]

In the video, the guy tightened the bolt, then gave the head of the bolt a good tap with a hammer.

Assuming all of the mating surfaces are flat then all that is required ae annealed washers.
If that doesn't work then there is a problem with the mating surfaces.

 

[bosco659]

Assuming all of the mating surfaces are flat then all that is required ae annealed washers.
If that doesn't work then there is a problem with the mating surfaces.

In the video I think that’s what he was trying to address, in particular, remanufactured calipers.

 

[gggGary]

here's a good a place as any sorry for the barge. ;^)
Neighbor's virago; replaced lines but wasn't happy with a "lack of slack" on the lowers, ordered next size up. Sucked fluid out through the bleeders till I got air. changed the lines. Refilled reservoir and sucked with a vacuum pump on the bleeders til I had only fluid coming out. Pumped the lever several times. Then with no lever pumping, cracked open the bleeders til fluid just showed at end of nipple, was back to hard lever in less than 10 minutes. It kind of surprised me how easy that was. Virago now back at neighhbor's place, good riddance ;^)!

 

[5twins]

For a minor leak, I'll loosen the banjo bolt slightly then re-tighten it. Often this cures the leak. Also, many times a slight leak at assembly will be gone the next day after sitting over nite.

 

[bosco659]

For a minor leak, I'll loosen the banjo bolt slightly then re-tighten it. Often this cures the leak. Also, many times a slight leak at assembly will be gone the next day after sitting over nite.

I should try that next time. I would be concerned that the original torquing of the bolt would induce hardness into the washer and retorquing would have less effect on the now hard washer. I guess it’s worth a try though. On my recent front brake work, stopping leaks was best achieved using Dowty washers on the stubborn connections. I also used aluminum washers (supplied by Russell Fittings) that seem to work well too.