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So I just purchased a 2002 Yamaha f50tlra. When I first purchased, it would start with the throttle lever half open but would blow black smoke. I cleaned the carbs out, bench synced the butterfly valves, installed a new fuel pump, new spark plugs, tested the prime start which functions correctly and tested the fuel enrichment system which also functions properly. Tested spark which is within spec. Engine timing is correct. Compression is within spec. I set the pilot jets 2 1/2 turns out and I'm still having the same problem as before, engine only starts at half throttle and runs super rich. I tried messing with the air/fuel mix screw but they don't seem to effect engine idle very much. I also hooked up my vacuum gauges to the intake and all 4 cylinders are reading 5 inches of mercury. Any ideas where to go from here? TIA