Bike stalls (not dies) when quickly given throttle?

[BillyThekiid]

Bike rides fine, but when I give it a quick rev, it bogs down for a sec then revs up to normal speed. When I slowly rev it, it does fine. Is this normal? 82 Honda cm250 custom.
Also , when gearing up, I occasionally hear one loud clink noise coming from the gear box. Any ideas?