Your's sounds about right... might want to check the clutches, they may need cleaning at the least or replacement parts (rollers, bushings, bearings, springs, etc..) at most, another thing to check is your carb settings (jets and clean those passages)..
Was having sorta same problem on my '03 Indy 500, starts up fine and bogs on take off until get past certain RPM, found out I needed to raise my needle (lower the E-clip) to get enough fuel through from idle to about 1/4 - 1/2 throttle.
'03 Indy 500 sks (Scumpman's Kicka** Snowmachine) extended skid/track to 136" from TracksUSA, AC roller clutch, Holtzman Tempaflow, clutched and geared, 2" risers, skidplate, old Pol rack.