I had previously tightened all accessible intake system connections, as I had mentioned. I think this tightening in very large measure sealed intake leaks and the smoothed rough idle, rather than, tactfully, airflow meter adjustments which can both cause and smooth erratic idle, in my experience.
Rough idle occured with cold engine, as I mentioned.
Warm engine exhibited no noticeable change below 4k rpm in engine operation, as I mentioned.
Why and how, specifically, does the engine stumble upon oil-filler cap removal?
I wonder how one would measure/improve the thermal efficiency of the engine: Egt, cht, mpg, compression test, spark plugs, timing, top overhaul? I have not explored hotter spark, probably unnecessary. Best power is typically a rich mixture, best economy considerably leaner.
I believe, despite your conclusion to the contrary, I have leaned the entire fuel map rather than enriched it. Mpg figures and wiper base points and spring settings and idle bypass settings and color of exhaust pipe and plugs support this belief. The base wiper setting is now leaner than stock, and barely moves and causes no rpm change at idle, by observation. As mentioned, by observation at current tune at speed minute wiper deflection leaner breaks up engine, richer speeds up engine. Pressing the starter button below approx.3.5k rpm results in rpm increase. I have made these observations with the airflow meter uncovered, connected to plenum, harness connected, and engine running on center stand. Please post your more precise test apparatus. I do not have a dynamometer. I had previously restored the airflow meter to its original settings, as you recommend, burned a few tankfuls and observed no increase if not a decrease in mpg. A lean fuel map may not increase mpg.
Thus my experiment.
Further reading:
https://itinerant-air-cooled.com//viewtopic.php?f=50&t=7761Oil cap removal at idle resulted in a vapor leak out of, rather than into, the crankcase, which indicates crankcase pressure higher than ambient, and such removal implies, contrary to my assumptions, less rather than more vapor inhaled into plenum via crankcase vent post-oil filler cap removal. I suspect engine idle stumble post-cap removal is due to wiper position change (intake air change negligeable?). Next time I have bike running and airflow meter on bench consequences of oil-filler cap and/or vent-to-plenum removal to wiper will be obvious.
The purpose of this exercise is to achieve a smooth running bike and the best possible mpg. Bike does have a full fairing, tall windshield. Neither brakes, bearings, nor transmission drag. Cars pass me regularly. The fun/dollar quotient of this machine is already high, your high mpg figures lure me.