OK, after waiting four weeks for new rollers we put in a set of 26 gram Dr. Pulleys. The shudder has gone away and the bike is much smoother at low speed. The trade off is the bike is geared noticeably lower at all speeds. I rarely have an opportunity to cruise at greater than about 100 kph in this country, however, so it's not the problem it would be for a U.S. commuter. Typical highway cruising speeds are between 70 and 90 kph, which has the bike between 5000 and 6000 rpm. 100 kph was around 5500 rpm with the factory rollers, but the shudder and vibe at 2500 to 3000 rpm was alarming. The jump from the factory rollers to 26 grams is a big difference. I would have chosen a 28 or 30 gram set if I'd had a choice, but I couldn't find one.
To substitute for the special tool to hold the pully we fashioned a steel ring with two bolts welded to it in the right positions and used a chain vicegrip to hold it still. We probably could have just put the chain around the pulley, but we didn't want to take a chance of bending or banging up the aluminum cooling fins on the pulley.
Thanks for all the suggestions. If anyone knows a source for 28 or 30 gram Dr. Pulley sliders for the 500 I'd probably buy a set and try them.
