My Huasheng and 5:1 4G on SBP kit tops out about 35-38MPH, depending on wind and what I'm wearing. My top gear ratio is about 15.3:1. HP peak is at 35MPH, redline is 40.
I usually cruise 20-29, but when I get a nice tailwind I find myself cruising about 32 or 33MPH.
Edit: I just noticed this is in the 2-stroke section. Oops!
I managed 42MPH on 2 different bikes with 2 different chinagirls using the same 34T sprocket.
My 4-stroke bike had a 2-stroke in it once, just a 44T sprocket tho. I never pushed it over 28.