loosing power on spree

[catsailor]

My 84 spree with a Taz big bore all of a sudden lost power. After 2000 miles I figured it was the plug, so I changed it. New plug did nothing. Cleaned carb, reeds, and sent high preasure air through the exhaust. I also cleaned the air filter. She ran as she usually does (35+mph with lots of power) for a mile or so, and then I lost all power again. Up a medium sized hill i had a hard time breaking 10 mph. Slow increase to 20 mph on the flats. I got her home, and did the same cleaning that I had done prior. Within 2 miles, the same problem again. This sucks because the season is quickily coming to an end here in new england and I would love to get another month or 2 of riding in. Any ideas? Did a plug chop after the initial good cleaning, and it was cardboard brown. Did one after the loss of power, and it was black, and full of carbon/oil/gas.

[catsailor]

anyone?

[Bear45-70]

Compression test before all else.