Hi Tom, just reading up the posting to your initial problem being of running rich, sooty plugs and black smoke in the exhaust. It sounds like you have made good progress with jet changes... good.
Running rich can mask other issues that weren't apparent before. Can you elaborate on coughing, sputtering in the 2>3k rpm range?
Is the engine falling flat as you move up the rev range? Does the engine reject the intake charge by popping back up the carbs? This will not sound as dramatic as backfiring in the exhaust, however it will hurt the throttle response.
Are you accelerating hard when coughing and sputtering happens?
A bit more info will help formulate additional suggestions.
Cheers
Ian
Running rich can mask other issues that weren't apparent before. Can you elaborate on coughing, sputtering in the 2>3k rpm range?
Is the engine falling flat as you move up the rev range? Does the engine reject the intake charge by popping back up the carbs? This will not sound as dramatic as backfiring in the exhaust, however it will hurt the throttle response.
Are you accelerating hard when coughing and sputtering happens?
A bit more info will help formulate additional suggestions.
Cheers
Ian