So, I posted here a couple weeks ago. Just thought I would give you a follow-up and help out others with the same problem. Brief history: I have an '83 XL600r with 7,000 original miles. Test drove before buying and everything looked good - no smoking, etc. Got around to changing the oil (used Valvoline 10w40 conventional motorcycle oil) and she smoked like a beast. I had added about 2 quarts (per the manual) and made sure I didn't overfill. The smoking subsided after around 5 minutes, but upon startup, it was terrible. A suggestion on this board was to try a heavier weight oil. Over the weekend, finally had a chance to change oil. Used Castrol 20w50 conventional motorcycle oil. Oil level is between high and low - no overfill. Now, very little smoke on startup. A little when I lay on the throttle until she's warmed-up, then nothing. Wow, who would have thought a small change like oil weight would have made a difference.