If the RC51 has stock final gearing, yes, changing the final ratio to 15/41, 42, or 43 will make a lot of difference.
There's a world of difference and riding style between a 600 and the RC51.
The RC51 comes into the torque curve starting around 4500 RPM and the power starts around 6000 RPM.
The main problem I have riding the RC51 on the street is that the streets are too slow.
These baby's like to run and it feels criminal to hold a tight leash on them.
It's so nice to find a long stretch of road and just cruise at 120 MPH (albeit rarely these days).
The sound is so nice. Not high-pitched like an I-4, more of a drone.