I checked the sparkplug today and it looked fine. Not fouled or caboned up at all.
I had a Onan generator that has a 5-1 C.R. but I sold it. I bet that would run biodiesel too.
Keep in mind the lawnmower was running about the same speed the whole time and the motor was under load because it was some thick grass ! 
Biodiesel and E-10 mix right away ! No problem mixing them.
Thanks, Steve
Greengirl Labs Florida USA Home of the Canoe Paddle Processor http://www.biodieselnow.com/forums/t/19664.aspx