A bit lengthy but please bear with me, just making info as complete and accurate as I can. 1974 850 Cmndo. The engine starts and runs well through full RPM range...until the plugs start to foul...within 30 miles. I am running twin Amal 932's that I have overhauled. New slides, 3 position needles, main jets (standard 220's), floats and float needles. Synchronization between the two is good. Tri spark ignition with ign. pack, fresh plugs and leads with proper resistance...set dead nuts on at 28º BTDC. While overhauling the head this fall, I went back into the carbs as the combustion chambers and plugs displayed rich mixture in color/deposits. Upon reassembly I set the needles at their upper most setting, looking for a leaner offering. The carb work was meticulous. Idle jets clear with smooth operation throughout. Reassembled everything and fired on 3rd kick. No air leaks around the fitting faces. As I rode and started and tweaking the air adjustment screws to find an acceptable mixture I noted how far in the air adjustment screws needed to be turned from recommended 1.5 turns out, 1.10+ back in apprx., thus enriching the mix. I attributed this, partially to the K&N air filter allowing more air intake. Popping gone, decelerates smoothly, good throttle response. Dirty/a bit sooty plugs found when starting became difficult. My next step is to adjust the needles one setting, to the #2 position, richer, and reset the air adjustment screws to 1.5 out from seated and see where that takes things. I have other ideas but would like to hear from those the have been there - done that. I have a clue as to how carbs work, Holley's, Webers, SU's. I really like the simplicity of the Amals and know there is a sweet spot in there somewhere. I would like to find said sweet spot rather than getting pissed off and end up sitting on the curb beating my dick with a brick because the beast won't run or start. Thanks for reading.