Anyone know whats happening here?

[Zephyr_Pete]

Hi Guys,

Appologies for the long winded post.

A while back I fitted new front pads to my zephyr 750, immediately after there was significantly more travel in the front lever, to the point where it can almost come back to the grip.

Since then I have fitted a new master cylinder seal kit, new piston seals, freed up the slides and blead the system many times with new fluid (The main Kawasaki dealer has also had a go). All this has had absoloubtly no effect.

Today I bought some brake cleaner and freed up the bobbins as best I could whilst still on the bike, by spinning with an M8 nut and bolt method gently nipped up. This also had no effect, but admitedly the bobbins were pretty siezed before this.

All I could think is that air must still be trapped in the lines somewhere. So I decided to clamp the hoses just below the splitter to try and eliminate where the problem is coming from.
The odd thing was I clamped the left hose and the lever felt perfect and back to normal, so i thought the problem must be something to do with the right caliper. I then removed the clamp and clamped the right hose, again the lever felt perfect as it used to be.

http://farm5.static.flickr.com/4124/5004496899_4daec14474_z.jpg

I then completely removed the clamp and the lever went back to being spongy. This one has got me beat, and any help on what going on would be much apreciated.

[newnut]

get some steel braided hoses. should fix it, maybe your lines are perished.

[CBRowner]

Sounds like air in the brakes but you've had them bled a few times now :-?

Have you checked the lever? There could be something going on in that area.

Apart from stripping it all down again, I can't think of what else it could be especially as a main dealer can't do anything :o

[Zephyr_Pete]

I think braded hoses will be my next try. The main dealers solution was to fit new discs at £170 each, as mine are aparantly slightly warped. This seemed a little drastic as the problem only occured after fitting new pads, and I want to be sure ive tried everything else first before I concider spending that sort of money.

[CBRowner]

I've heard of this problem happening before but I've so far never suffered from it, although I need to replace my pads soon but I have a few months of braking left in them.

Hopefully you get it sorted soon [smiley=thumbsup.gif]

[CBRowner]

I just thought, have you tried moving the clamps around to find if it's a problem along the pipes?

It may be worth starting from the bottom and clamping it avery inch or so until it becomes spongey or not, that way you'll know if it's your pipes [smiley=thumbsup.gif]

[Zephyr_Pete]

Good shout, i'l give that a go. Braided lines seem the way forward to me, even if thats not the problem.

[CBRowner]

Another option would be to put the pipe, at regular intervals, into some water to see if there's any bubbles. You could also do that with your caliper just to make sure that the problems not coming from there [smiley=thumbsup.gif]

[Zephyr_Pete]

Just tried to pinpoint the problem area further. I started by clamping the bottom of each hose individually where it meets the calliper. Still get a firm leaver, same as clamping the top.

http://farm5.static.flickr.com/4147/5005576000_c5afbd5f27_z.jpg

Seems as if the 2 calipers work fine individually when isolated, but dont seem to be sychronised and work together to give a firm lever.

[newnut]

have you checked to see if any of the pistons are leaking fluid? they are like your front forks, pitting, scoring or knackered seals will cause your problem, especially after changing pads as you've moved the pistons back further than they have been for a while. braided lines always help firm up your brakes. take the calipers off you need to check for any leaking fluid, give them a good service while they are off. brake cleaner etc. hope that helps.

[Snowy]

If the problem started only after fitting new pads it's likely to be connected. Fitting new pads means pushing the pistons back so if you didn't clean them up first you could have pushed a load of grunge up into one of the bores and a piston is sticking. It's worth taking the pads back out and gently pushing the pistons back out and giving them a good clean and maybe some copper grease. Also by pushing the pistons in to take the new wider pads will raise the level of the brake fluid in the master cylinder so make sure it's not overfilled now. Clutching at straws I know.....

[Thorkill_The_Tall]

Whatever you do, do not use copper grease on your caliper pistons, as it will affect the seals and cause failure.
Use a silicon based rubber grease.

How old is the bike? Are they the original brake lines?
It varies from manufacturer to manufacturer, but if your lines are more than 5 years old and not braided steel, you really should change them.

Other than the curious effect you have described with the clamping, I would have suggested raising the calipers above the master cylinder when you bleed them. You'd be suprised how tricky air can be to get rid of, sometimes.

[Jon_W]

When you bleed the brakes, the bleed nipple must be the highest point on the caliper or air will remain inside the caliper. You will also need to ensure that there is no air in thr loop between the calipers.

Have never used clamps so cannot comment on this method. You'll need to pump the brake lever on fresh oil to build the required back pressure for the cylinder to operate correctly. This can take some time but eventually the prressure will come.

[t1pper]

I have to agree that it is connected with new pads as thats when the problem occured first.
Are the pads seated properly and flush to the caliper piston and brake disc, maybe you have a slight wear lip on the edge of the disc and the pads have a long way to travel before contact with the disc proper, meaning a longer stroke on the lever.
Isolating a caliper at a time will half the amount of travel required at the lever (as it is only half the fluid movement) giving a slight false impression of improvement. If you can get a firm lever on a second pump I would suggest that is this is because at that point the pad is fully pressed home against the disc and the excess travel has been compensated for.
Probably clear as mud :D
T1pper

[t1pper]

Just to sumerise it got to be down to excessive travel somewhere at the caliper or pad end of things. Especially if you have checked and serviced all other items. Additionally if your stock hoses were ok before brake pad swap they should be ok now, replacing them with braided will only show minium improvment to lever travel.
T1pper

[Cemorah]

Had something like this on my GPZ500. Often, apparently, new piston seals can take a while to settle in and can stick and therefore pull the pistons back creating a lost movement of the piston. Try building as much pressure as you can with the lever and then cable-tye it closed to the handlebar. Leave it like this for as long as you can 24-48hrs as long as curiosity will allow.

It worked for me

[Mark_Able]

Had something like this on my GPZ500. Often, apparently, new piston seals can take a while to settle in and can stick and therefore pull the pistons back creating a lost movement of the piston. Try building as much pressure as you can with the lever and then cable-tye it closed to the handlebar. Leave it like this for as long as you can 24-48hrs as long as curiosity will allow.

It worked for me

Yep, used to do that on the old Trumpet 750's we had at CSM years ago. Does work... [smiley=thumbsup.gif]

[nicko@able]

Have you tried the "over night bleed"?release the master cylinder filler slightly,cable tie the brake leaver back as tight as you can,go to bed.the pressure in the lines can force any air back up and out the top.Worth a go perhaps,It`s worked for me in the past.

[Zephyr_Pete]

Cheers for all the help guys. I'l try tying back the lever again, but for a couple of days this time. Last time it made a big improvement but didnt last long. Il trying losening the lid this time too.