I just worked on a stock 650 AVS2 for the first time last weekend. It was on a very mild ZZ4 Chevy in my neighbor's Nomad. Man that sucker was rich at idle! Which I understand. Rich is safe from the manufacturer's perspective, but holy cow my eyes were watering.
Advancing the initial timing a few degress helped clean it up a bit. Thankfully my neighbors bought the metering rod/spring kit. After checking the fuel pressure and messing around with the rods, I got the plugs burning clean. It just took me a few hours to get familiar with it.