-Shift shaft isn't womped out on the claw end?
-Is the shift shaft wobbling around in the case? Does it need a bushing in the cases
-Eccentric bolt is adjusted properly?
-Are the shift forks bent or worn?
Horrible idea for any trail machine. The weight helps maintain inertia when navigating trails and turns. If it's not strictly drag on a lighter set up its wasted effort in my opinion.
It's vibrating bolts loose, so that's No Bueno. The major problem I see is that there's a bolt that came out that's not visible. You need to find that... Or disassemble it and verify that it's not in there.
Hello oddball exhaust port....
Don't stress over the residual rust in the ports. Tends to happen on alky bikes. Especially if they're not purged. Get some photos from different angles. Just seeing that exhaust port, I'd assume they are some type of drag port.