Thanks for the confirmation on unleaded. My panic is subsiding.
On carburetor gunk, on old bikes which have been sitting a long time, I have come across gunk which laughs at todays enviromentally friendly spray cleaners. Some Auto parts have a can of liquid carb cleaner you can soak the carb in and Yamaha has a carb cleaner I have heard realy good reports on.
The bottom line is that you should examine the jets under a bright light and a nagnifier and make sure they are clean.