Slightly warped rear rotor - '82

[mcgovern61]

While we were restoring the '81 Standard, one thing that took me by surprise is how easy it was to move around the garage or even outside. My'82 has always been a real "slug" to move around. It feels like it weighs a ton and I always have to learn froward to get her going with the engine off. Now, granted, I do have aftermarket bags on the back, but otherwise the '82 is also a standard. She always rolls when I let the clutch out easy enough, but I always thought she came to a stop a bit faster at slow speeds than she should. Brakes are not really dragging per se', but something is not quite right. I know the rear rotor is a bit warped, and I mean only slightly. Hardly enough to even feel at the pedal. No real pulsing.

Back when we restored this bike, the rear brakes were dragging and locking up because the aftermarket exhaust that was on the bike at the time was interfering with the return of the brake pedal. It heated the rotor a few times enough that when I rotate the wheel by hand I can barely feel the wheel slow a bit. But, when turning by hand (up on the centerstand), it does take just a bit of effort to get the wheel spinning and it will stop right away.

I had checked the rear wheel of the '81 on the centerstand as a comparison and that wheel would keep on spinning. I determined that the warped rotor must be producing enough drag to slow the wheel but not be causing the brakes to heat up the rotor.

 

[mcgovern61]

I know the rotors cannot be turned traditionally. But I have heard they can be ground. So........I thought I would at least try to grind them a bit. I have a large right angle sander that has a disc on it that is about 80 grit metal. I forget what the disc was for (obviously for sanding) but I have had it since 1983 when I sanded the bottom of my wooden boat. The metal in the disc is strong. I have been using the disc for years to sharpen my lawn mower blades. Works great on metal!

So, pulled the caliper out of the way, started the bike, put it in 1st gear at idle and fired up the sander. IT WORKS! :yahoo:

I only let the sander grind the high spots (set up like a lathe). It smoothed out the outside of the rotor nicely. Unfortunately, I cannot get to the back side of the rotor the same way. :hihihi:

Re-assemble the caliper, step on the pedal to re-set the pads and cylinders and spun the wheel. The brakes release normally and the wheel is spinning freely now! :yahoo:

I put the whole bike back together and took her for a ride. For the first time since I have been riding this bike, she rolled down the street with the clutch pulled in and didn't come to a stop on her own. Now I am feeling so foolish........

I should have picked up on this sooner. I always complained that I rarely get more than 35 MPG except on the highway on long trips were the average can go up to 38-40 MPG over a long trip. I hope my mileage improves now at slower speeds. :fiddle:

 

[dan filipi]

I was just looking at mine how I could surface the front disks both sides without pulling them off. Front break is terrible. I gotta do something with it.

 

[mcgovern61]

I'll post a pic of my sander and disc to get an idea.