OK what year bike? Mikuni or Keihin carb? How long on set of rings? Stock jetting? Stock reeds? Type of fuel? (race gas, pump gas, av gas) Type of oil?
Gotta have some specifics.
In general it sounds like jetting. 60:1 is pretty rich for any synthetic in a trials engine. A broken reed will cause this kind of bog as will a plugged pilot jet. First step I would suggest is a disassemble and clean of the carb.
Did this just start or has it been a long term problem?