Oops.. Duct tape wont work on brakes

I am getting closer to having the old girl running and got my next to last batch of parts in. Rebuilt my master cylinder, got new pistons and seals installed and a new braided brake line on the front wheel. Bled out the system per directions on Old Britts web site and THEY WORKED!! First time in at least 15 years and pressure held on the front disc, I was happy as a hillbilly who just married his first cousin! I found a leak on the brake switch which just needed a little tightening which cleared that up and even the brake light worked. After I got all that worked out I got sick and have barely been out to tend to anything new in the last few days (that is how my wife knew I was sick) but a few days ago I noticed there was some brake fluid leaking so I started tracing down the problem when I noticed fluid leaking down the rotor on the outside. I was pretty sure what the problem was so I ordered new piston seals. Tonight I drained the fluid, disassembled the caliper and here is what I found:







Thankfully the inside seal is good so I will just have to wait until my new seals come in and be really careful putting the piston in. Read on Old Britts site that he usually cleans up the edges of the piston to prevent this but the ones I got were beveled so I thought I was good. May go ahead and try to smooth the edges some more so I do not have to deal with this again!

Should have my oil tank back form CNW in a few days with new grips and a filter to fit to the top of the tank to vent to atmosphere. Once I get that, should finish up all the double checks and hope to fire the Norton up by this weekend!! I will get pics of the tank up and will probably video the first attempt cranking her up. Just hope I get to feeling better soon, this cold is kicking my but, cannot do much for long without getting exhausted.

If anyone has any tip on getting the piston in without having this happen again I will gladly take your advice!!

Just to put some color in, here is how the bike sits now. Still have it on a lift to finish checking things out (rear wheel alignment, chain tension, oil line routing, etc.).



Garage is getting tight for space since we are still sorting boxes from our move and my wife going through cancer treatment. Hope to have all this cleaned out this summer and dedicate this area to my work space for the bike and my mustang.

Hope the Norton is a stress reliever for both you and your wife.

I have replaced rusted up pucks in two Combats with SS ones just wet with brake fluid to slip in with new seals in the grooves. No issues on hard use. Do keep eye on fluid level and evidence of leaks at the master cylinder blown away riding but can let brake go completely away one good pull down to the next.

Liberally coat the seal with Girling rubber grease prior to assembly - there are also other brake assembly lubes that are impervious to brake fluid, but don't be tempted to use vaseline or other mineral type greases not meant for this application.

Sorry to bump an old thread, but the second photo above is exactly what the nick on my brake seal looked like. I was just wondering if you had any suggestions on how you solved the problem?

The replacement new pucks should be smooth enough as is not to abrade or nick seals installing but I hedged my bet by polishing pucks by buffer wheel. I'd be hesitate to use anything but brake fluid as lube. There must be some friction grip of the seals on the pucks for the seals recoil to retract pucks just off rotor or they will drag and heat and boil and fade. Might try warming caliper and cooling the puck for a bit extra clearance but I or most don't seem to need too. Best wishes on enduring through the move and wife and bike recovery.

davecox2 said:

Sorry to bump an old thread, but the second photo above is exactly what the nick on my brake seal looked like. I was just wondering if you had any suggestions on how you solved the problem?

Click to expand...

Lot's of lube, and the FEEL as you assemble it. A rotating/rocking motion generally allows the seal to ride up over the radius as needed. The feel is different from the failed one in the image above.

Re: Frustrating brake issue

Postby ZFD » Tue Jun 25, 2013 6:32 am
You need to put the outer piston in first, then the seal, then push the piston backwards from the centre of the caliper towards the outside over the seal. Piston has a rounded edge on the closed side and a sharp one on the open side

Well, I finally got it to work! Turns out there was a tiny piece of gunk in the inner groove that was preventing the seal from seating properly. I took her out on my first test ride with front brakes around the neighborhood. All I need now is a taillight and mirrors and she'll be ready to get plates.

hobot said:

Re: Frustrating brake issue

Postby ZFD » Tue Jun 25, 2013 6:32 am
You need to put the outer piston in first, then the seal, then push the piston backwards from the centre of the caliper towards the outside over the seal. Piston has a rounded edge on the closed side and a sharp one on the open side

Click to expand...

Brilliant! I'm just about to assemble my caliper, so I'll be using this technique. I assume you just saved my outer seal.

Nater_Potater said:

hobot said:

Re: Frustrating brake issue

Postby ZFD » Tue Jun 25, 2013 6:32 am
You need to put the outer piston in first, then the seal, then push the piston backwards from the centre of the caliper towards the outside over the seal. Piston has a rounded edge on the closed side and a sharp one on the open side

Click to expand...

Brilliant! I'm just about to assemble my caliper, so I'll be using this technique. I assume you just saved my outer seal.

Click to expand...

Yep, it worked great! No leakys! Thanks, Steve.