I posted a bunch of jetting info on speedzilla (dukepilot) and SMJunkie (huskysm610) for the SM610. Here are my current settings with LV full exhaust, some additional holes in my airbox cover and backfire screen removed:
JD Red Needle at 5th position
Fuel screw about 1.5 turns out
Boyesen pump plate
Power Now Plus
This is at sea level.
Also installed one of these with adjustable main and slow air circuits for fine tuning. This helped me eliminate most of the popping on decel.
With this combo of goodies on my carb, it pulls hard from down low with good midrange and decent top end. I'm happy with this setup and it is much improved from stock.