http://www.yamaha-motor.com/sport/accessories/acscitemdetail/5/348/1218/5375/2009/all/4335/0/detail.aspx 12 hours on OE unit and I just installed this one today. This should be done ASAP. Got to ride a few hours this afternoon at my riding spot and trail loop, then for about 30 mins on my turn track at home. I immediately noticed off idle, it was far smoother. The engine vibrated less, and it was a very positive feeling. I had a huge grin on my face about a mile into the loop as I noticed I could run a gear higher and lug it to my hearts content. This is why I wanted a large displacement 4 stroke! Large improvement in chugability for such small dollars. Everything else in regards to drivetrain is OE. It could be placebo effect but, at both places, I noticed a reasonable traction increase. My riding loop has at this time 10% sand/ 10% hardmud/ 80% hardpack. Being in my age bracket, and the time of year, the "Wedding Circuit" begins this weekend. So, my riding time will be limited in the coming week, and that makes me feel like this.