I'm currently running the ZingerPro 22x10 and getting right at 6500r's. This kind of puts the engines in perspective, with Robert getting 7100 with a 21" and the 6500 with22". I may give the 21" a try sometime soon. I almost wonder if I can lean out the top end a fuzz. I did lean the low end just ever so slightly to clean it up a bit, that made a big diff. I do agree though, it is ballistic for a little 50. Shoot, these small engines have more power then some of the motorcycles we used to ride.

Here's my install, it's just a quick pic I shot ...