demetris74 wrote:
My MC21 boogs at 6-7k, power valves work fine.
i have 140 mains, i made the airbox mod. This goes away when i remove the filter foam, then the bike runs clean.

That would certainly indicate a rich mixture. As Stephen says though, it depends on the how the bike acts regarding throttle position (and load of course), which part of the carburetion system you need to tune.
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