Front brake faint low-speed pulsing

[Motorhobo]

The 94K75 I'm working on has a faint pulsing when the brakes are applied at low speed. For instance, if you're approaching a stop and apply light lever you'll feel a perceptible surging with each rotation of the wheel. It doesn't surge or lock up at high speed or when the brake is applied with any force. It's as if the disk were warped and I would accept that but I had the same thing on my 95K75 before I rebuilt the calipers and put on Spiegler steel brake lines, and now there is no surging at all.

The brake lines on the 94 are rubber and have DOT markings on them, which leads me to believe they're not the OEM lines that shipped with the bike. I'm considering putting Spieglers on this one, too. I don't know when the lines were replaced and recommendation is every four years or something like that.

So the questions are:

1) barring warped disks what other causes of surging are there that could be eliminated by steel brake lines and caliper rebuild?
2) How can I determine if the brake lines are the original ones or have been replaced since the bike came off the production line?

Thanks for any input --

Van

[tg4360]

Stock disks or aftermarket?

I have EBCs on mine and found that if I got the drill pattern "out of phase" so to speak, the light pulsing went away.

TG

[Motorhobo]

These are stock. I know I'm not the only one with this -- has anyone else had an issue with their brakes feeling like the disks were slightly warped?

I read an extensive thread about this somewhere -- I'll try to find it.

[tg4360]

I also read a very interesting article (I will try to find the link) from someone in the industry who stated that most "pulsing" is from pad material deposited unevenly on the disk for various reasons.

He said that if you can't find any actual runout outside of the listed limits that scuffing the disks and re-bedding  the pads might clear it up and even gave advice about how do do so with several hard stops from speed etc.

[Motorhobo]

Thanks -- I'll see what I can find on it. I wonder if something as simple as swapping the pads left/right would make any difference? All I know is it went away on one of my bikes and I don't know what I did to fix it.

[drut]

I had the same on mine:low speed/light application pulse.Freed off calipers (2 x slightly sticky pistons) & all is OK! Thought I had a warped disc or a disc high spot but sorting calipers cured it.