I was stuck around 42 with the stock one speed engine
I also have a 15 15 sha. metal screen with a foam cover now and #68 jet
with the bx26 and the 10 inch rear wheel im around 45
and also it wheelies pretty damn good with the 10 and stock drive belt and top speed is around 40mph
I can do the whole block, when it hits the power band it pulls the front up without even trying!
a buddy of mine has this kit on a 2 speed express. it does 44.7 or sumthing
and talk to david cox! he has a lot of experience with these water cooled express's