Hi Terry,
Not sure what motor you are using but our HS or Honda motors don't rev to 10,000 RPMs. My EZ bike is geared 15.48 X 1 and my tackometer reads 8700 @ 40 MPH with 24" wheels. My 26" test bike is also geared 15.48 X 1 and it touches 40 MPH @ 8000 RPMs.
If you are geared @ 5.54 in the secondary [50/11], and 5 X 1 in the primary [using American math] the final ratio would be 22.72 X 1. 22.72 X 1 @ 35 MPH the motor would be turning at least 10,300.
Maybe the front isn't 5 X 1 or your GPS might need to be checked. If your numbers are correct I fear for your motors life.
Are you using 30" wheels?
Do you have a tachometer installed?
Keep us posted on your findings.
Have fun,