White smoke from left tailpipe

My 78 KZ650 has been running like a top until about a month ago. I was riding it around town one night, and after I got up to speed, I had a nice old blue haired lady pull out in front of me.

I did what I always do; clutch brake shift, but, instead of going down one gear, I went down 2 gears. When I let out on the clutch, my back tire did the nice "i can't spin faster than the engine will let me, so I'm going to leave some marks on the pavement to remind you of how bad of shifting you just did" thing.

Now, whenever she starts, I'm getting puffs of white smoke from the left tailpipe. It's very noticable on startup, and after about 5 minutes of riding, it seems to disappear.

What are some things to look for? I'll try to get a video to show you guys (if ya need it), but, it may be a few days since it's been raining around here every stinkin day for about 2 weeks.

Thanks in advance!

IMO there are only 2 candidates for this problem.

Valve seals and piston rings.

I favor the valve seals, since it goes away after starting.

Fairly easy fix.
I believe you can replace the seals without pulling the head.
More on this technique if asked.

sounds like a guide seal if it only happens at startup;)

I'm definatly askin. Anything I can check for specificly to make sure it's the valve seals? Or did I just set myself up for a smart answer of "yes, the valve seals.."?

I've got the clymers manual, but, not with me, so, I can't take a gander through it to check.

bad valve guide seal will allow a little bit of oil to leak down valvestem when motor is shutoff into combustion chamber which will burn off when you start the motor,rings on the other hand will normally smoke under a load;)

If it were my bike I would be changing the valve seals.

All the other possibilities involve more work, and are less likely to be the problem.

I think you have the delorian syndrom, riding too close to the white lines.
have you run a compression check? and I would check the valves clearance before I just pulled the head and changed the seals