Originally Posted by grizz1

Don't know if you have the long or short low speed needle version, but what you describe is a classic symtom of the long needle carb being tuned TOO LEAN ON THE TOP END. If you are running a long needle carb, richen the top end 1/2 hour at a time until the bogging goes away.
For full long needle carb tuning instructions visit the Tech Tips section on my web site - www.go-racing.co.nz.
If the low speed needle stays in the receiver jet even at full throttle, then you have a long needle carb. If it pulls out at aroound 3/4 throttle, then you have the short needle carb.

If you have the short needle carb, then you may be too lean on the bottoom end, or you may have an air leak in your fuel or pressure line somewhere perhaps. If it was running good before and you haven't touched anything on the motor siince, chances are it is something external from the motor.