Front Brake System Advice

[fizzer6hundred]

Background: 13K on bike (original brakes/pads). Now the bad news I dropped the bike backing down an incline. All seemed ok but the front breaks seemed different. The front brake seemed to have more travel/position when fully engaged almost to the throttle. I figured a quick adjustment might help (boy was I wrong!!!). So I looked at the adjusting screw on the brake lever. It was fully screwed in but had the stop nut on it. Therefore if the screw was to be tightened any further the nut would need to be removed. I thus removed the screw took off the nut and put the screw back on and screwed it all the way in. So the levor was now effectively more engaged to the master cylinder. I thought I had enough free play as it did not seem tight (first big mistake). Well long story short the bakes must have been partially engaged and heated up to the point where the front bake locked up and caused a crash around a turn.

Rider ok but bike plastics and peanut cover messed up (NRC makes sand cast peanut covers for the FZR which I recently purchased).

I put the lock nut back on the lever but noticed (after I purchased a front race stand) that the wheel drags a lot. So I removed the pads and the wheel spins free now.

Observations:
Drag detected after incident
Removed pads wheel spins free
Calipers seem ok no detected leaks

Questions:
Do you think the excessive heat from having the bakes engaged that caused the swelling and further compression subsequent lock up damaged anything from all the heat? If so what do I need to look out for? I will check my rotors for both run out with a dial indicator to make sure I did not warp them and also check for wear on the rotors by miking it out but I am most concerned about the calipers. If they are not leaking could they have heated and become sticky causing the pads to be so tight? Should the wheel with new pads spin as free as with no pads meaning how much friction if any do the pads have when in the caliper and seated properly? How do I verify the function of the caliper other than re-assembly with new pads?

[taggy]

Firstly make sure nothing is warped or bent.re-blead with NEW fluid as it is possible you got air in it if it was over far enough to allow some from the reservoir into the line, strip out the calipers and give them a good clean, make sure the pistons move freely in and out without the pad in, but don't go too far or they will pop out! copper slip the rear of the pad where it hits the piston. Check that you don't have a leak in the master cylinder or have managed to wrench the lines or reservoir enough to break a seal at the banjo bolts or reservoir. Hopefully just re-bleeding will help!

[fizzer6hundred]

Thanks Taggy I am curious if the brake hydraulics is a closed system how does dumping the bike create a potential leak?

[ragedigital]

I doubt heat would do any damage to the calipers or rotors. There are people on this site who put them through much worse at race tracks.

Certainly sounds like you may have bent the rotor. I would certainly check them for warpage.

You might have also damaged a brake line. Replacing them with Stainless Steel lines and new fluid should take care of it.

[DonTZ125]

Heat from dragging brakes will most certainly warp your rotors, cook your seals, and vapour-lock your fluid. Racers use their brakes hard, but they get right back off of them just as fast, and have enormous cooling flows.

I agree with Rage on this, though - you may have done physical damage to rotors, calipers, or mcyl. Air can enter through the reservoir when dumped, or you may have cracked a connector loose.

[taggy]

It's also possible that you wacked the lever into the m/c seal and did it some damage!

[fizzer6hundred]

Ok guys your a big help (I mean that).

I just measured the run out with a dial indicator on the rotors....Good news there the run out is +/-2 thousandths on each side the rotors are NOT warped.


Taggy you maybe also correct the brake lever is ground to the point that half the end (ball part) is ground off. The MC I am sure took a beating. I will have to check that as well. Have not got to the calipers yet but have ordered some fresh EBC pads:

Plan to:
1. clean the calipers with brake cleaner
2. inspect the calipers and pistons for movement to make sure they are not frozen
3. replace pads, purge all the fluid and replace and bleed out the hydraulic fluid
4. check for leaks
5. test dynamically on the stand for clearance and lever freeplay
6. test drive carefully and cross my fingers.........

Does this seem like a good plan?

[taggy]

don't forget to check everything is done up tight, i had a problem with the r1 m/c on mine and it was just the tiniest tweak of the bleed nipple that cured it. I mean just so little that you hardly noticed the movement! Before you undo everything take a good look and dab some tissue paper on any joints nd see if it comes back wet, might give you an idea if anything is leaking/has leaked.

[fizzer6hundred]

Thanks Tag,

Hey another question whats the best way (tool) to compress the pistons so I can slip a new set of pads in? I know its got to be compressed flat on all sides so it slides strait and true. Like a C-clamp with a thin piece of bar stock?

[yamaha_george]

Thanks Tag,

Hey another question whats the best way (tool) to compress the pistons.............................................................. Like a C-clamp with a thin piece of bar stock?

Fizz,
the darn tool self

be careful not to shove them too far in and make sure the pistons are clean so they do not bind once pushed in.

[fizzer6hundred]

Ok things progressing, I have cleaned the calipers and compressed the pistons so I can get the new pads in. One questions before I start flushing the old fluid and bleeding. What position should I set the front brake adjuster screw on the master cylinder? This is the one that started the whole mess (see beginning of post if needed). I am asking this because the last setting was all the way in on this screw with the nut still in. This would be the most compression to the piston on the master cylinder that can be adjusted (I assume for more worn brakes). Hence my assumption is that I need to back it way the hell out to give me the right starting point to get the free play in spec.

anybody know what I mean and have the advice I am looking for? It should be simple for those that do their own brakes........

[fizzer6hundred]

Ok more progress more issues....I figured out how to set up the MC adjustment screw to give me the correct free-play. The brakes are all done but the new problem here is the pressure on the lever indicates it needs more bleeding. I spent 3 hours bleeding the darn things with a Mytec vacuum puller, the right caliper seems to show bubbles all the time. The left caliper seemed to be fine. Since the bike went down on the right side and the right front brake lever almost sheared off I can only assume that the MC internals may have been damaged. If this was the case I would think both calipers would be problematic but the left "seems" to purge air well.

So my question is this: Is there a systematic way to isolate a caliper or MC for leak? On this bike we do not have a MC bleed nipple which would make this problem a breeze.

[yamaha_george]

On this bike we do not have a MC bleed nipple which would make this problem a breeze.

Fizz,
you have answered you own question at least part way. Do as I did and buy the longer banjo bolt that holds two fittings and use that on the MC.
see:-
http://www.saltmine.org.uk/fzr/frontbrakes.html

that at least will let you be sure that some part of the right hand side is damaged !

[fizzer6hundred]

Thanks George, so a double banjo would split the circuit at the MC? The original circuit is much more complicated. Do you have a diagram of this circuit you used? Also it seems like the MC should have a bleed screw as many modern bikes now do. I wonder if I can just add one some how or replace the MC with a better units and keep my calipers stock. I know this is not rocket science but dam its got to be right as our lives depend on the front brake being near perfect in my mind.

[DonTZ125]

When you buy your double-banjo, be sure and get a double-banjo with bleeder...