I'd like some more info on this if you have it. I know a chap who had a new gearbox (warranty) at 24,000 miles and then again at 48,000 miles (Warranty). It seems ok now though and he said he never used to use the cluth on upshifts. Honda mec told him its something to do with undercuts on the gears being reduced on newer models
It has been explained to me and I saw the wear on the parts from my bike. But I cannot remember the exact names or reasons why the bike was popping out of gear.
These square shaped parts get rounded corners over time. I think these are the "dogs" on the gears. The rounding off of these corners cause slippage and the transmission pops out of gear under acceleration. The popping out of gear causes damage to the shift forks and/or the rod that the shift fork rides on.
Like I said, I can't remember the exact description.
When I had my tranny work done, they replaced first gear, second gear, and third gear, a shift fork, the shift drum, and some other parts I can't remember. It cost $1080 in parts and labor.
I had a Factory Pro Shift Kit installed. This makes for more positive shifts and is supposed to reduce the likelihood of rounding off the dogs in the future.
15000 miles later and so far so good, but it does feel like the aftermarket Factory Pro spring is losing some of its tension.
I did not have the gears "undercut". "Undercutting" is not necessary and is a track, performance modification for the most experienced racers. It is not worth the expense even for agressive street riding.