15,000 miles on FM 107 build. For mellow acceleration I generally shift into 3rd in low 30s, 4th in low 40mph, 5th in mid 50s and 6th @ 70mph. All depends on conditions, how much quick response I need in traffic.

Lately I find myself shifting later and running her in higher rpms. For example, cruising in fourth gear at 50-55mph instead of shifting into 5th. The engine seems to like this.

Wondering if a well broken-in engine might "enjoy" the higher rpms? Not sure if the question even makes sense. I don't have a tach on the RK so I can't be more precise. Maybe I have been babying the engine all along. Any opinions about this? thanks.

 

3rd in low 30s, 4th in low 40mph sounds like lugging to me. Follow your instincts and keep it where its happy

 

loose motors (either well broken in or built that way) are the way to get power.
there is a trade-off of short longevity. Widened clearances reduce friction and incur more movement (or float) of rotating and reciprocating parts. Heavier oil will help delay rebuild. For now enjoy your ride, you know how it's been and what it is now.
oh, I agree with the above thes twins like to be kept in a higher rpm range, designed to work that way and lugging is actually bad for these motors.

 

Sounds like you are finding the power band in the upper RPMs. Where the power band is depends a lot on cam characteristics.

 

thanks guys. I sort of feel like I have been riding her like a *****. It's not that I have lugged the motor, and there are certainly times when I wind it out. But now I run it much longer through the gears before shifting, and am less prone to shift if I am up in the power band. After a couple of seasons it feels like I am getting to know my machine for what it is. Or at least understanding how the 555s are meant to preform.