Brake rebuild & laziness

The old, neglacted '83 XJ750 Maxim I have been bringing back to life had dodgy front brakes. I rebuilt both calipers & the master cylinder. The bores of all 3 items were unscored so I cleaned then up with crocus cloth. They looked just fine then.

The caliper piston seals & dust seals were fine as were the 2 cups in the master cylinder. Reassembly was done & I bled the system. I could not get a hard lever no matter how many time I bled them.

I was annoyed. I have been bleeding brakes for more years than I care to count. Bought a complete used, sealed set (calipers, lines, junction box & m/c) from this forum & put them on instead. They were just fine.

Been working on the unsatisfactory set over the past month or so. Pulled then apart, reassembled them, bled them (clamped on my workbench) but still the same sponginess.

Today I removed the 2 bleed nipples, wrapped their threaded portion in Teflon tape, replaced them & again bled the sytem. Still spongy!!!!!

I have a Mityvac pump & all the vacuum bleeding accessories but had been too lazy to get it out. Decided to give it a try. Eureka!!!

Got a lot of air from one caliper that did not come out with regular bleeding. The vacuum pulls the fluid through quite fast so you have to keep a very close eye on the m/c level.

Brakes now not at all spongy. I now have a complete, sealed spare setup.

Moral: I will try not to be so lazy next time

 

I've managed to do my 650 without a pump, but it took 3 days. I think maybe the Maxims are extra hard because of the rise coming out of the MC.

I've had better luck by turning the bars hard left. That tilts the MC and gets the outlet closer to level.

 

I did hold my m/c in my vise (soft jaws) & tilt it so the air would want to come out of the small holes. Quite a bit did, eventually.

It seemd to be one of the calipers that held onto an air bubble.

I will always use my pump now that I have seen how easy it is.

 

One thing someone suggested to me was to cable tie the brake lever to the grip overnight to allow the air to rise out...

No idea if it works or not :lol:

 

Thanks for the info!!. I know it doesn't take but afew bubbles to make the brakes spongy and sometimes they are so small, you don't see them.

 

I've also managed to shake extra air out by tapping the banjo bolt at the MC with a mallet.