We just switched to Yamaha Sr. this year and so far we haven’t noticed much change in the lap times. Our Jr. engine made about 19 hp at 320 lbs. Now we our making about 22hp but weigh 360 lbs. My Daughter said she likes running the pipe more midrange in the turns but I think the extra weight we are caring balances out the extra power we make. Not much time on the pipe yet to really come up with conclusive results but this is what I’ve seen so far. Is everybody else seeing the same thing? Or do I not have it figured out yet?