4K @ 55mph, hmmm. That means it has 4500 rpm left to redline. Sounds like you need to twist the wick up a little. That's below half of recommended max rpms, right in the middle is where that little fellow is starting to run good.
If you see it on my bike I did it
Current ride 05 1500 Classic FI
lovin' the new scoot
"When all is said and done,usually more is said than done" UNK
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XI waited patiently for the Lord; and he turned unto me, and heard my cry.