Actually, the fluctuating duty cycle is good news (no faults).
The fact that it is a little high means you are running lean. Try to bring it down to 45-55% using the adjustment screw.
Procedure will be found doing a search.
Good Luck

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified