Topic: Brake bleeding grrr

[Hush]

OK I'm still working on this 1989 CBR400RR for my son, it's coming together nicely and after stripping it right back to the frame it now looks like a bike again.
I have struck a very very annoying front brake problem, my son insisted on powder coating the calipers (and just about every other part of the bike) and I had a hell of a job to get the new seals in, I have fitted braided brake lines and just to day fitted a repair kit for the master cylinder.
All good things, if they worked!
For all my knowledge of brakes and bleeding I cannot get this bike to give me squat!
The brake lever remains as limp as a eunik's donger!
Bubbles, yes I have those, every time I think I have it sussed I get more micro bubbles, I've used all the tricks I learned off this site plus a few more, nada, nothing, squat!
For a bike like this that is one step back from a track racer and is barely road legal I must insist my son has really good brakes.
Anyone got a foolproof method I haven't tried yet???

[kghost]

Hi hush,

I know your quite experienced.

I sometimes let them sit overnight between bleeding.

Seems to coalesce the micro bubbles.

They didn't powder in the piston bores I hope.

Sometimes when completely dry I start bleeding at the splitter on the triple tree and work my way down.

[surveywaters]

    You guys know what you're doing, just wanted to say I really like my hand vacuum bleeder. It cuts the job time and makes it an easy one man, plus seems to get those hard to reach bubbles.

    On another note, I had a bike with a funky angle on a banjo. A bubble would develop there and could only be removed by loosening the banjo bolt.

[fendersrule]

Harbor Freight has a professional grade (believe it or not) vaccum bleeder. It was the best $30 I've ever spent there.

[Hush]

All good advice guys, and yes they did spray into the piston chambers, I think I got it pretty good and fitted new seals but as I cannot get any movement out of the pistons I'm going to remove them and strip them again.

[LesterPiglet]

I always bleed at each connection in the line. I also raise the caliper/s above the mc for the final bleed. Also if needs be, tie the brake lever to the handlebar overnight after bleeding, I believe this lets micro-bubbles work their way to the MC. I haven't used any speed bleeders so cannot comment on those.

[kghost]

All good advice guys, and yes they did spray into the piston chambers, I think I got it pretty good and fitted new seals but as I cannot get any movement out of the pistons I'm going to remove them and strip them again.

I have never had a good time when that's happened.

Bit of stripper on a small brush will get in the bores......

[RAFster122s]

Hush,

Sorry if I am repeating things or something you have tried. From brief description I am not sure what you have tried.

If I understamd correctly, they powdercoated the inside bore of the caliper? The piston needs to be able to slide out of the caliper bore when the seal is not fitted. If it cannot do so easily when you invert it, then this is likely part or all of the issue.

Is the master cylinder pumping fluid? Cracking the banjo at the caliper will give you fluid leaking there when you squeeze the MC brake lever of course.  If it isn't then remove the line on the MC and squeeze the lever and hold it. Put your finger or thumb across the line fitting to seal it and release the lever, repeat until you get fluid to pump out of MC.
Naturally, protect your paint during all this and wash well areas exposed to the brake fluid.

[Xnavylfr]

I have always bled from MC down,, remove banjo at MC and place thumb over mc hole and pump till it squirts your thumb off, then hook up line ,then go to next banjo fitting and do the same(Keep the MC full) hook that line up the to next connection ,probably the caliper, do the same on that banjo fitting till you squirt your fingers off, then hook to caliper then bleed from the bleeder valve.  If you get enough pressure behind that caliper piston it WILL MOVE!!


Xnavylfr(CHUCK)