Re: 40 MPH Club
The first time I hit 40 on a motorized bicycle was with my first build on it's second engine back in '07. I had a laser-cut adapter I designed that used the older-style large-bolt kit ragjoint, allowing me to bolt 110MM BCD sprockets to the ragjoint without removing it. I started with a 39T, ended up with a 34T. My top speed was 42MPH, which was ~7500RPM. That engine was on the very edge of survivability at that RPM, and it did eventually start knocking in the upper end. My 2nd build used yet another chinagirl and also attained 42MPH with the same sprocket.
I blew up the first engine going 30 with the 44T. That one started knocking after a few runs over 6K RPM. Many chinagirls just shouldn't be run much over 6K if you want them to live for awhile. Some people get lucky with a great engine out of the box tho. My 3rd chinagirl was such an engine.
All that said, I'm not going to believe over 9K RPM out of a stock engine. Only the very best rebuilt chinagirls like RSE and Arrow can do that and live.