TOPIC:

Every once in a while, while I'm really letting it rip in second gear, it pops out of gear. I can shift back into it again right away but it is a little unnerving. Is it a sign of clutch wear? I ride a '78 650b

Uh, probably not a clutch problem...it is possible that is a bent shift fork.

Sounds like second gear might need to be back cut or replaced. These are known for this, mine did it so bad shifting from 1st to sec on a wheelie, it would jerk back and forth rapidly. I back cut my own but wouldn't reccommend it. Always check the forks while it's apart. I couldn't use second gear on mine it got so bad.

Congratulations!
Your about to get very well acquainted with your bike.
You need to split the cases to change either second gear or the whole transmission.
Second gear is the weak link in almost every make of motorcycle.

I had that problem before with my 78 KZ1000 and had to split the cases.
When I did I found that the circlip had came off the shift rod because the groove was not cut deep enough.
An easy fix once I got to it.
Same symptoms, the bike would would still shift, but it would pop out when I was getting on it.
If this is the problem you will see it right away and it is just a matter of cutting a deeper groove and using a fresh circlip.
I am lucky to know a good machinist.
You don't have to pull out the gear cluster or anything real tricky.
And if somebody says you should dress up the first gear while you have it that far apart and he'll do it for cheap
"Don't do it", but thats a story for some other time.
Good luck JD

normally if a transmission is popping out of gear it means the shift dogs on that gear are worn out it most likley means second gear on both shafts will have to be replaced or at the very least if they aren't to badly chewed up undercut

Hey rkan,
How many miles you got on that thing ?

It's got about 24k miles. Today it did it again right as i was about to shift at 8 grand and the motor wound up to maybe 11k rpm. My buddy behind me said that black smoke came out the exhaust right then.

"i was about to shift at 8 grand"...

Am I understanding this correctly where your running in 1st gear up to 8Krpm to shift into second!

All the time! That's the fun part!

Haha well I was in 2nd gear about to shift into 3rd and it was on an on ramp.

shift faster!