from my post on an earlier thread:
"I always flip or change the front sprocket about every oil change. (Front sprockets are only $19 and are very quick and easy to swap out. Front sprockets should also wear out about 3 times faster than the rear sprockets, i.e. according to the gear ratios.)" I only flip the sprocket once, then I throw it away (after 12,000 miles) since they are so cheap and so influencial on the chain wear.
As for the cush drive, I have a couple of thousand miles on homemade inserts. There are 5 identical inserts, one in each section, behind the straight portion of the original cush drive. These inserts are small tabs (about 1 by 2 inches) I cut from a rubber baseboard (about 1/8th inch thick). This baseboard was made to cover the bottom of a house wall where it meets the floor and can be bought from Lowes' or Home Depot or a lumber yard. I have less than 1/8th inch "slop" in the cush drive now, and it shifts gears better than when the bike was new. Cost: $4 total.
