About the most common reasons you get a bent shift fork is if the bike goes down on the left and catches the shift lever.
It can also happen if clutch-less shifts are made without an ignition cutout switch.
And to a lesser degree if trying to force an engagement of a gear.
Usually, if a fork is bent it doesn't completely engage the dogs on one side and that gear can pop into a false neutral under power.
On the side where the fork is bent over to, it causes heat buildup and wear on the groove the fork rides in. If the heat buildup is too great, it will require replacement of the gear and fork.
I've seen this on some bikes where the side of the fork and groove in the gear were blue from heat.
However it sounds like you're having problems with the shifting mechanism: ratchet, pawl, detent wheel, return spring, or shift drum as you're not getting a distinct "click" of the detent wheel dropping into the inset of the shift star on the drum when it rotates (or not rotating properly).
The way to check out the shifting mechanism is to remove the right side cover.
To get to the mechanism is to remove the clutch basket.
Then you can inspect the overall shape of the pieces.
If everything looks good and you suspect it's in the gearbox itself, then the only way to that is to pull the engine and split the cases. Not a minor job.
I would put the bike on a rear stand and test shift the bike (engine not running) to see how smoothly it shifts by hand. Maybe it will shed some light.
You may remove the right side cover and inspect for broken/missing pieces, but most are going to be behind the clutch basket.
Last edited by SubSailor; 12-14-2009 at 09:30 PM.