Front Brake Caliper Advice

[Neilw]

Hi,

I need some advice.

My front brake Caliper is leaking fluid where the pipe enters the calliper assembly. Under pressure, brake fluid oozes out. I fitted a new copper crush washer when assembling the brake, but it wasn't sized perfectly for the hole. I also replaced the piston and seals with new ones and used the stock size, which was the same as the one I removed.

I don't think the calliper is the one meant for this bike (1978 CB550 F2), as I have ordered replacement bleed nipples from two outlets and received two that were much smaller than the one on the bike. Also, the pipe going into the calliper is different from the stock part.

The pipe has a 10mm thread, and I used a 10mm x 14mm x 1mm crush washer.

I intend to keep the setup as is, but what sort of washer and size should I use to get a good airtight fit?   

Cheers
Neil

[Oddjob]

Oh dear Neil. You do seem to get the problems. First off the bleed nipple isn't correct for the bike. It should sit much higher up and use an 8mm spanner, yours looks like a 10mm. A lot of these calipers suffered from the bleed nipple snapping off due to rust and they tended to be drilled oversize and a bigger nipple fitted, sometimes it works, most times it doesn't. The other one is the inlet for the brake line. You've fitted a set of braided lines, nothing wrong with that, however in the hole where it goes is a small sort of tophat washer, if someone has removed that your buggered. The adapter you have fitted is shaped to fit that tophat washer so as it tightens it seals against it. No crush washer used, the tophat washer is essentially the crush washer. Remove the line from the adapter, it's possible it's fitted upside down, see if one ended looks dimpled or inset. That's the side that goes into the caliper.

Let us know what the result is.

Ahhh, you've added more pics. The adapter is flat sided at the bottom. Remove it and check the other end.

Take a pic looking down the hole in the caliper, lets see if the tophat washer is in there. Looks to have been helicoiled.

[Neilw]

Yeah, I've got a Frankenstein of a bike; I'm so close to getting it ready, just one thing after another. Good job, I'm made of stern stuff!

The bleed nipple is 10mm, and it's operational, so that is good. The braided lines came on the bike; all I've done is cleaned everything and installed new piston and seals, and added that crush washer, perhaps without i would get a seal?

Pic looking down the hole. 

[Bryanj]

All the 250G5,360,400,500,550 calipers are the same so should be plenty out ther to fix but try without the washer to see if it seals on the cone fitting first

[scottly]

Is the fitting bottoming out in the hole before crushing the washer firmly?

[scottly]

This is what the "cone" fitting looks like. It's actually a seat for the stock flared pipe fitting, and is normally removed to use a banjo bolt type with a crush washer.

[K2-K6]

Are these caliper machined on that flat (surrounding the bore) to takesuch a washer, and seal correctly?  Is the seal original point down in base of the bore.

To aneal (soften) the copper washer, heat to red with gas torch, then drop straight into cold water. Will give best chance of accommodating surface irregularities.

[scottly]

When I converted a K7 750 caliper, which is similar to a 500/550, to use a banjo bolt with crush washer, I machined the surface flat so the washer would seal properly.

[Neilw]

All the 250G5,360,400,500,550 calipers are the same so should be plenty out ther to fix but try without the washer to see if it seals on the cone fitting first

I have a front brake; removing the crush washer I added was the trick!

Thanks everyone!

[Bryanj]

Scotty, i have seen that part on a 750 but never managed to find one on the 500/550, it sounds like that fitting is now sealing on thee cone

[scottly]

The stock hard pipe going into the calipers had flare fittings on each end, with an inverted cone to seal on the steel cone down inside the caliper, as well as inside the fitting on the hose end. It is/was standard procedure for hydraulic brakes to use flare fittings.
I had some adapters on early 750 calipers with a matching inverted flare to fit braided lines, but Neil's adapter appears flat on the end. Also, the cone appears to have been removed in the pic looking down into the hole?