they had a rule change last year so they can run inline fours up to 600cc, belive it or not the 500's still battle it out up the front.
I swaped him my dirt kart for 3 CR500 motors.
If you've got photographic evidence of 500 2 strokers in unusual places, post away...imagine a CR500 in a took-took in Indonisa, that would be funny.
