Rev 3 Rear Brake

[slogger]

Many have helped out and commented/advised on my dilema so sorry to labour this one but it really is doing my head in.........

Long story short, rear caliper seized during a comp and overheated. Was never 100% happy with the rear brake so have set about overhauling it. Changed the pedal assemble and refurbed the master cylidar with a rubber kit. Attempted to refurb the caliper but one pot would not go in even without a seal so suspected that over time the overheating had warped the caliper body slightly. So purchased a brand new caliper and pads from Lampkins and attempted to fit that a few nights ago. Have spent 3hrs bleeding it with and can not get decent pedal pressure. Am getting full movement on the pedal without it going completely solid. It will just lock the rear if rotated by hand but not under load.

Have deglazed the pads/disk using the usual get heat/cool down method but the problem definately appears to be lack of fluid pressure to moke the pots adequately. The only thing that has not been changed is the brake hose from the caliper to the master cyl so I am going to replace this. I did strip the new caliper to make sure the pots moved OK and they did?

Am really stumped and would appreciate anyones thoughts?

[grahamjayzee]

Slogger, you have my sympathy! I spent the best part of 3 weeks trying to get rear brake pressure after a rebuild. There has been much written on here about the problem, and really, it's all true!

It's (almost certainly) air in the system. The problem is that with the brake in situ, there are many trap points, and the master cylinder doesn't shift much fluid with each stroke. The result is that each stroke moves the bubbles, but they never get over the high points before you have chance to make another stroke, so they simple stay put.

What did I do to cure it? I used a huge bucket full of patience!

Take the whole system off the bike and hang it from some point. I used a point on my garage ceiling so I could hold the master in the vice and therefore pump it. It didn't seem to matter if I forced with a syringe, or pumped through (I think this is because the system is spoiled by TINY amounts of air and as such whichever way you fill it, you still need to bleed out the tiny bubbles). When I had the system hanging I'd tap it from time to time and keep rotating it so the trap points where moved. I think it was in this position for about a week with me tapping and pumping every evening! It's worth pumping using a rod of some sort in the m/c rather than the pedal as you get a longer stroke.

Don't pump too slowly or the air doesn't shift, but resist the temptation as you get frustrated (which I'm sure you already have!) to pump away like a maniac as this causes the fluid to cavitate (froth up) and you'll make it worse.

Patience my friend, it WILL firm up eventually!

Graham

[slogger]

Hi Graham,

thanks for the prompt and comprehensive reply.........

How much hassle is it to refit in a fully assembled state??? their does not seem much space as an end to end so I assume their is a level of dis-assembly of other bits to put it back together in one piece?

Rob

[anotherfive]

Hi

I'm on my fourth beta so here's my tip.

wheel off pads out. force pots back into caliper and lock in place with a couple of spanners wedged in or a couple of G clamps.

This reduces the hiding area for air. Open up the top up tank and slacken off bleed nipple but cover end with light pressure with a finger. Three hands needed but use pedal or a rod to work the m/cyl.As you work it two things will eventually happen oil and air will squirt from the nipple and the level will go down. Keep topping it up. Youll know when all is air free as the squirt becomes stronger. Nip up the nipple, pads back in wheel on and continue the pumping until pots and pads take up the play simplesss!!Let us know how you get on

[grahamjayzee]

Good tip, Anotherfive.

As for re-fitting the whole assembly, you need to take the airbox off. I think I had the subframe off as it gives you lots of room then. It's not too hard though.

Graham

[scorpa250]

Hi I had a nightmare with my sons rear brake same as you it over heated and i thought i would give it a complete rebuild seal kit in master cylinder seal kit in caliper.... all to avail.... to cut a long story short (about 3wks of swearing at it) i asked a yamaha factory mechanic and with all the information i told him he told me to get a new complete master cylinder and use a car vacuum bleeder system and it worked !!!! hope this is will help you .Paul

[matt_urban]

you need to force lots of fluid thro the rear brake a top cap with a pipe coming out and a syringe should do the trick

[slogger]

All.

thanks for your support and advice on this. Have ordered a 100ml syringe from ebay to try the reverse bleed method. Will let you know how it goes.

Still surprised even with a new factory calliper how stiff the pots are in the calliper???

Does anyone lube on re-assembly? Some people swear by rubber grease, others brake fluid, others wd40?????

So much conflicting info.................

[matt_urban]

silocon lube i have found the best

[stork955]

Gday, if you want to lubricate any brake parts only ever use rubber grease or brake fluid. Anything else will destroy the rubber seals. Also never wash brake parts in any solvents. Hot water only. I wouldnt lube a new caliper - it already is!

Cheers,

Stork

[slogger]

I wouldnt lube a new caliper - it already is!

Not the way this one is moving......................

Came in a sealed Beta bag, but the pistons are tight. It takes a good push with BOTH thumbs to move them in.

[stork955]

Gday -thats normal. The seals act as a return mechanism for the piston as well as sealing, so they need some "firmness". Have you got it bled yet?

Cheers,

Stork

[whiz]

Hi

We have had Beta`s for years and there is not one answer to your problem, I`ve come to the conclusion that they all work but the real

answer is luck.

what I now do, is split the caliper, remove the pistons and carefully fill the caliper with fluid then very gently push each of the pistons back in, this is not easy as they have to be really tight for them to work, but only to the point where they have entered the seal, ie a couple of mm then when you have all the pistons entered ease them in in rotation as gently as poss

untill all the way home, you should see air being pushed out, then re-assemble the caliper making sure that all oil ways are overflowwing with fluid. fit the caliper to the bike and bleed the rest of the system before you fit the pipe, end of pipe in a container full of fluid and pump till there is no air, make sure you have the caliper full of fluid then fit the pipe, fingers over the end untill last minute, fit banjo, slowly pumping as you tighten it up to get rid of air and the jobs a good un.

The air in my experience always gets traped in the caliper behind the pistons where it can move about and not get expelled.

This may not work for you, as I said it seems to be down to luck and perseverance.

All the best

Whiz

[slogger]

Had another try tonight reverse bleeding with a 100ml syringe. More bite but the problem definately appears to be too much pedal travel + not enough pressure to the pistons.

Did try this starting with the pots fully in and also out to a reasonable amount with fluid behind them.

Observed the pots moving in the caliper once bleed (with the pads out) and they all move out under pressure, between pedal up and pedal down move in and out about 2mm each. The inner pots are not moving as freely as the outers but if you lock the outers the inners do move fully out

Whilst air seems like the logical reason, the amount of times I have bled them I must have hit "luck" once and had no air in the system and the problem is consistent every time.

The only parts of have not changed are the master cyl (although this has been re-rubbered) and the brake line (from the cyl to the caliper)?

Would appreciate a photo of an 03 rear end to see the amount of spare in the brake line. Mine does seem to be overlength and I wonder if this is a bodge from the previous owner.

Once again, thanks to everyone for thier tips, I am slowly attempting each method but my hunch is still a component ? its to consistent ........

[stork955]

Gday - no, its normal. Beta rear brakes are really hard to bleed. The problem is that its really hard to get the master cylinder primed, so it will move fluid. Then its really hard to get air from all the high points in the system. My old Techno also had a blocked transfer port in the master cylinder which makes priming and bleeding impossible. If you can force fluid through the reservior inlet with a syringe the transfer port is OK. The only way i got mine was to remove the entire system and hang it up as someone mentioned previously. This way you can orient things so air will rise up if that makes sense for you. You cant bleed these with the pedal, you must remove it and use a screwdriver or similar. The M/cyl piston must return fully to the circlip. You will have to roll things around to get the air up and through high points. Tapping with the handle of a screwdriver will help this. Patience is needed... Once it is bled, refit the lot back onto the bike and away you go. I cant comment on the Rev's, but on the Techno I had to undo the top shock bolt to slip the hose in. Not hard, all things considered.

Cheers,

Stork.