[sliver]

Just finished a full front end conversion on my single disk 2000 m750. 996 forks, rotors and brake calipers. The brakes feel fine until the bike rolls a few feet. Then the lever pulls back almost to the grip. If I pump the brakes a few times it returns to normal. I think the rotors might be warped and are pushing in on the pads as it rotates. Has anyone seen this before.

 

[Andrew_Cornett]

Sounds more like air in the brake lines to me. When the air pocket reaches the plunger your lever goes completely to the grip. You pump like mad forcing fluid down and the bubble rises giving your brakes back.

I would bleed the brake lines again.

 

[sliver]

The strange thing is the lever feels perfect till the bike rolls a few feet. I have tried bleeding it several times-no air bubles stiff lever- roll bike a few feet and the lever goes back almost to the grip. Pull in the lever once or twice, not pumping like mad and the lever feel is back to normal. Everything is fine till the bike rolls. This is kicking my **s.

 

[CRASH!]

It sure is strange. I can't think of anything that would cause the lever to pull in by itself.

You win on "stump the chumps."

 

[s4strati]

Just finished a full front end conversion on my single disk 2000 m750. 996 forks, rotors and brake calipers. The brakes feel fine until the bike rolls a few feet. Then the lever pulls back almost to the grip. If I pump the brakes a few times it returns to normal. I think the rotors might be warped and are pushing in on the pads as it rotates. Has anyone seen this before.

the rotors would have te be pretty seriously warped to apply that kind of pressure on the pads. when you roll the bike a couple feet, do you hear abrasion or do you feel resistance?

 

[stevey]

highly unlikely that a floating rotor would be warped that
bad. could be a seriously stuck caliper seal causing the
pistons to retract more than necessary.

 

[simcor]

I don't think warped rotors would have this effect. If the rotor was warped it would move the caliper pistons in on one side of the disc, and allow the other piston to move out of the caliper on the other side of the disc.
If the lever is moving in it could be:
* either fluid is leaking past the master piston back into the reservoir (incorrectly set-up piston rod position)
*air is still in the system somewhere (?)
* or lastly, as the rotor moves over the pads / caliper pistons, some leakage past the piston seals occurs allowing the lever to pull in due to loss of fluid.
Are you seeing any loss of fluid around the caliper pistons ?
...Good luck,
...Simon

 

[AlexB]

Definitely not the rotors.. you would only feel the pulsating rotors at speed and it would have no effect on the level pull (it might vibrate in sync with the warpage on the rotor, but that's it.)

Although I don't really know what it could be.

 

[sliver]

I talked to in parts atsomeone at Pro Italia. I was looking for a rebuild kit for the Brembo calipers (which Brembo does not make). I was told that they don't see many bad front calipers. I explained what the bike was doing and he said that it was a bent rotor or the rotor did not seat corectly. They had seen this problem before. I am going to put the frontend in the air this evening and try to check the rotor. Has anyone out there done a rotor swap or a single to dual disc conversion and have a extra rotor for a 2000 up monster or the 996 snowflake style that they want to sell? Just thought I should ask. Thanks for the help everyone and I will keep you updated.