I was amazed how hard the kick back was - I have very strong legs - I work out, ride cycle, and walk so I have good muscles - that may be why it broke two of my ankle bones, and two foot bones, but it ripped of a loose shoe, and threw that 40 ft in front of the bike, and my foot swelled up to foot ball size. Funny thing was, I was not straight legged, but tense, so my muscles held the leg still, and the kick back bent my foot up to my leg.. It hurt then, and it hurts now still. The ankle is not hurting much, now, just the top bone of my foot. It has taught me a lesson I will not forget - keep the timing spot on, and get a bike with electric start.
I am intending to lower the gearing of the bike, and turn it into a trials machine, start it by bumping it, and only use the kicker when I have to. I will probably go with an electronic ignition too, to keep it from doing my foot in again.