Okay, so I owe some pictures to my project thread.  Yesterday I installed the front brakes, among other things.  The caliper was filthtastic, so I cleaned/rebuilt it, which was actually not very hard.

When I installed it, I found that it somehow doesn't line up with the rotor very well.  With the mounting bolts on the fork somewhat loose, it feels firm as a brake should, but if I tighten those mounting bolts, it moves slightly (but imperceptible by me) such that when I use the brake lever, the caliper uses some of its force to push the rotor off to one side by like 1mm.  It's enough to make the brake feel spongy and bad.

In my hand, the calpier slides smoothly on the mounting bracket.  I greased up the pins in their rubber jackets just to be sure.

My theores are either the caliper is still not moving smoothly enough on its slide pins, or there is some miniscule difference between the 2001 and 2004 forks, or maybe my axle is bent causing the rotor to misalign.  Any other theories?

If it's a mechanical compatibility issue, you might be able to shim the caliper mounting bolts and make it line-up.

If it's pulling the rotor away from the wheel (couldn't tell from the post), you might be able to shim the rotor where it mounts; the other option is grinding a mm off of your caliper mounts, which could be... interesting.

Edit: checked Ronayers for part numbers on the different parts:

K1 right fork outer:   51130-01DA0
K4 right fork outer:   51130-01DD0

Doesn't mean the difference is in the caliper mounts, but it could be.

That's exactly what I was thinking, but I wouldn't know what needs to be done.  The fiche(s) for the two models calipers don't look appreciably different to me.  From how it looks, I have a hunch the caliper wants to be about 1mm farther from the rotor, which can't be done without grinding, and I'm not grinding anything on a hunch.

However, I just noticed that the front wheel spacers and rotors on the 2001 and 2004 have different model numbers, so maybe I need to take a look at what's different about them.  I have the 2004 RH spacer, so I can give that a shot, maybe it's 1mm longer and just what I need.

Could your lower fork tube be rotated a little causing the misalignment?

It is a stretch of an idea, but if the axle bolt were bent and the fender mount/plate  had very elongated holes...

I would loosen everything up on the axle and fender mount, apply the brake to align the pad/caliper with the rotor, and then try to tighten the tube parts up with the brake applied.

Then if you have misalignment, shim as needed or replace as needed.

I loosened the fork brace, but for some reason I didn't think of loosening the axle.  (Haha, even though I already said "maybe the axle is bent."  I'm a retard.)  I'll give that a shot when I get home.

Otherwise, I'll try to shim what I can... I wouldn't know what to replace if I wanted to replace something

You can't imagine how many times I bled the brakes before noticing that the caliper was moving! 

There is a spec on the axle runout. You can either check it with a (good) straight edge, or use the service manual method of a pair of V-blocks and a dial indicator.

The service limit is 0.25 mm (0.10 inch).

That's not much to fiddle with and the axle mount is really the only serious mechanical joint in the system beside the triple supports.

I would not put too much faith in that the parts have changed eventhough they have different numbers. It is common for Suzuki to change numbers with a change in models, even if there is not a change in the part.

You do have a semi-floating front rotor. So the rotor will be able to move side-to-side.

They change the prices, too!  I've saved real money by looking up older models on the fiche and buying those parts instead.  In some cases, the newer model parts are cheaper instead.  (About a $50 difference between the '01 and '04 rotors.  )

The rotor moves, for sure.  But when it moves back, it pushes the caliper pistons in a little bit, which makes the brakes really spongy.  At first I thought there was air, or that the brake line was old and turned to crap, but then I realized the caliper movement.

Just something to try:

Make sure the caliper bolts are tight.
Loosen the fork brace.
Loosen the axle clamp bolt (bottom right leg), and the axle nut.
Prop up the front wheel so you can spin it.
Spin it, and rotate the axle to where it drags the least.
Let the bike down.
Push down on the bars (do not use the brake).
The forks as they travel down the tubes should align everything.
Tighten the fork brace first.
Then the axle nut.
Then push down on the bars again (do not use the brake, again).
Then tighten the axle clamp bolt.

I got it.  It's this guy:



It's not that the caliper wanted to be shifted one way or another (which it should be able to do on its own).  It's that this bracket is bent, for some reason.  It actually torques the caliper at an angle when I tighten it up.  If I swap this piece from my other GS, the problem switches bikes, too.

Now there doesn't seem to be a number pointing to this, so I guess I can't buy it.  So now the question becomes, does anyone have a spare one of these?  Or can I fix it somehow?  (Implied: Can I figure out what's wrong with it somehow?)

There he is.  Looks okay to me. 

http://gsproject.codefarm.org/caliper_bracket.jpg