91 DR250S: 4lb, 3oz
98 DR350: 3lb, 15oz
The manual suggests jamming a penny between gears to stop them from spinning when you're trying to torque things down. I tried this to torque the flywheel bolt down (95 ft/lb) and I broke a tooth off the oil pump drive gear ($30 replacement). So don't try that.
When swapping the trannies I swapped all the internal parts (gears, shafts, forks, and drum). The reassembled trannies both bound up. I spent a long time trying to figure out what was wrong. I finally swapped the drums back and they worked. I examined the drums closely and couldn't find anything different about the two, but it appears the drum needs to stay with the case it was meant for.