A friend of mine has a '00 426F. He took it to the shop a few weeks ago because the gas left in it over the winter was not preserved and thus ended up varnishing the carb. The shop cleaned it and everything was fine at the time. When he brought the bike home from the shop he rode it around the block and it ran nicely. About a week later we go out to ride and he finds now that the bike will not run unless the choke is on. We even turned the idle screw to maximum with no success. It seems to be running rich - popping and sputtering at idle. Could it be a fouled plug? Keep in mind that the last time it was ridden it ran fine (arond the block). Any suggestions would be appreciated.