I decided to ride the SR out to the farm on Sunday and when I got there something made me look at the rear wheel area. What I saw was a crack in the rotor through the drilled holes out to the edge of the rotor. I took back roads back that evening night to minimize highway speeds. I shudder to even contemplate the result of a chunk of brake rotor breaking off at speed. I counted four cracks all the way out to the edge of the disc and two more between holes. There is enough lip on a couple of them to catch a finger nail. I'd bet that under a lot of heavy braking each section could warp differently causing other problems.
The Kawasaki part number I'm looking for is 41080-1020. Checking prices I found that Bike Bandit has just the rotor priced at $493 and Ron Ayers has it at $407. So, I guess I'll be trolling eBay and trying to locate the local bike salvage yards for a replacement. My dilema is that I can't be sure that a used rotor won't already have or soon develop cracks. With safety in mind, a new rotor seems to be the only sensible solution. In the mean time the SR will remain parked until I resolve this.
I think the lesson from this is to inspect every aspect of an old bike very carefully. I know I've looked at that rotor dozens of time in the past year, but I never noticed those cracks, even though they appear quite old.
BTW, the chain isn't that rusty, that's gravel road dust.
Enjoy the pix.
- Nate >>