When using an 18t front sprocket, use the following as a guide for chain length:
54t – 142 links
55t – 142 or 144 links
56t – 142 links
57t – 144 links
58t – 144 links
59t – 144 links
Changing from a 520 size chain and sprockets to a 415 chain and sprockets on the R3 makes a significant performance improvement.
I specifically dyno tested this upgrade to prove the difference. These 2 dyno runs are done back to back (about 20 minutes apart, as fast as I could pull the wheel and change the chain and sprockets) with the same bike, settings, dyno, tune, everything identical, and in the middle of the day after lots of other runs so the bike and dyno are hot. These are each the best of 5 runs to be sure everything was even. You can clearly see that the 415 kit improved power to the ground by .62 hp and torque by .29 ft lbs and improved performance across the entire power band.