Right side disk won't center in caliper slot

Beginning of the season, got a front flat in the garage, so put the wheel from a parts bike on. Last week I changed both front and rear tires, put the original front wheel back and discovered that the left side pads needed replacement. Ordered parts, changed the pads yesterday.
Right side pads had a good bit more material...but one side was worn about a mm or so more than the other. When I put the new pads in and reassembled, after squeezing the brake lever the pads contact the rotor fine, but the rotor isn't centered in the slot, and the outboard side of the slot drags the rotor a bit. How do I fix this?

 

Had a similar issue with my right caliper when getting it back on the road and looking at stuff closely that i hadn't done before. The disc wasn't central, the caliper mouldings were slightly different right c/w left on the inner side where it mounts to the fork. Just a little thicker on right side, i filed it down a little. Now it's centred. Maybe you just hadn't noticed it before ? And i doubt a 1mm difference in thickness will cause any problems.

 

-The "movable" fork (whichever side doesn't have the axle nut) may need to be adjusted "in or out" on the axle slightly;

-Your calipers need to be rebuilt. The 750 Seca uses the "holding block" style caliper; the caliper needs to be able to slide in relation to the holding block in order to compensate for pad wear. What happens is the little pin boots fail and the sliding pin gets all rusted and corroded and the caliper can't slide against the block like it should. This causes the brake to drag, accelerated pad wear (which you saw) and the likely chance you may overheat and warp a rotor.

Also, read this: http://xjbikes.com/Forums/viewtopic/t=41400.html

You can't simply change the pads.

 

I've already replaced the lines with stainless from Chacal. The caliper slides with firm hand pressure, I don't think that's the problem. Other side wasn't sliding as it should, that's the one where the pads wore out to trigger the pad change. This side still had plenty of pad material left, I wouldn't have changed them had they been on a single disk bike.

I found the diagram you posted here: http://xjbikes.com/Forums/viewtopic/t=4 ... build.html

..and I'm still confused, With the new pads, it appears that the rotor is pinched between the inboard/non piston pad, and the piston side of the caliper itself. This drags enough that I can turn the wheel with firm pressure, but it stops as soon as I stop turning.

For the time being, I put the thickest of the old pads on the inboard side, this gives clearance to let the wheel turn. I keep trying to figure out explanations, the only one that continues to make any sense is that the inboard/non-piston pad (both, actually, they are the same) is too thick. The right side pads worked fine, and there's no obvious differences between them,

 

The explanation that makes sense to me is to pull both calipers, disassemble them , clean them, polish or replace the slider pins, replace the pin boots, and replace the piston seals. Nothing else is going to correct your problem.

At the very, very least pull the slider pins and polish or replace them, and clean up the surfaces between the caliper and the caliper holding block (replacing the shim if needed) so it can all slide smoothly.

 

Lube the Pistons, Seal Channel, Seal and Cylinder Wall with Fresh Brake Fluid.
Use Medium-sized "C-Clamp"
Place a Socket that fits the Pistons I-D inside the hollow Piston.
Use a Coaster or portion of Vinyl Siding to protect Caliper Surface where Clamp aligns.
Apply the C-clamp to the Socket and outside Caliper surface.
Tighten Clamp, ... s-l-o-w-l-y.
Align Piston TRUE within Cylinder.
Horizontal and Vertical planes. Perfect. Fuss with it until its right.
Lube.
Tighten Clamp -- gradually moving the Piston back into the Caliper.

 

The caliper itself is NOT moving freely in relation to the holding block and "centering up" on the rotor like it should. Either that or its piston isn't retracting smoothly. The solution is the same:

YOUR CALIPERS NEED TO BE REBUILT. (Along with the master cylinder.) That IS the answer; as you'll eventually discover.

 

Yep a full clean and rebuild, tho what i said above was after a full rebuild with all parts in the right place and working smoothly.