Anyone know whats happening here?

[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
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.