Quick note re: the power issues... it was wonderful, fabulous when I started riding yesterday morning. I even managed to get up to 74 MPH on a relatively flat stretch! I was running along at 65-70 with what felt like power to spare, and actually passing people!
Then by around 11AM, we started losing oomph... I could only get up to 61-62MPH on flat stretches and it was driving me bonkers. It was down to 55MPH or so up hills again like it had been on Thursday. I had no idea what the variables could possibly be... the only thing we did between getting great performance and getting poor performance was I had flipped the fuel petcock from main to reserve, and then flipped it back and filled up with new gas. (Premium - it was 92 octane at that gas station.)
After I was having such bad performance, I started experimenting with flipping the petcock back and forth in case it was some debris caught in the petcock that was obstructing the fuel flow. It didn't help. At our lunch stop, I added some octane booster just to see. It didn't help. Toward 3PM or so I started getting the power back in little spurts... by the end of the day, I was running 72MPH again on flat stretches but it was pretty much full out.
Admittedly I've never tried diagnosing something like this before, but I checked the operation of the throttle body on the carbs while I was driving and they were definitely moving when I twisted the throttle. Something in my gut was telling me it was the air/fuel mixture... too much of one, not enough of the other. That's why I had Kay pull the spark plugs. I feel like those spark plugs are more fouled than they should be, which to me indicates that it's running rich... maybe we'll try putting in lower octane gas today and see what happens. (And yes, the air filter is fine - we swapped to a new K&N filter before we left Boston and we've only done around 1,000 miles on paved roads since then.)
So... I guess we'll see what happens today!