Your 2000 suzuki 80 RM keeps fouling the spark plug?

First of all, once a spark plug fouls it must be replaced with a new one. The plug is ruined and will continue to foul. If new plugs continue to foul, it could be too rich fuel mixture from problems in the carb. It could mean the piston, rings, or cylinder is worn and needs to be fixed, replaced or the cylinder be bored. Make sure it is not getting too much oil.