The Z250 is a great little quad for trail riding, but for the MX track, no way. I have no problem keeping up with the big utility quads going through the trails, but when I tried it out on the MX track I figured out that it definately wasn't meant for that. The ground clearance isn't too bad. Its better than most chain drive quads. I haven't had too much of a problem in mud. Pretty much you just have to plan your route, stay out of ruts as much as possible and stay on the gas and let the momentum get you through it.
And Chewbacca, I think 40 ft. table tops is stretching it a little bit. I've hit some 20's in 4th gear about 1/2 throttle. I can't imagine it having enough power and speed to clear a 40.

 

40 feet isnt really that much. plus if you have a good landing its fine. but the suspension is pretty good on it. i have mine on a tighter setting but its all good

 

Thanks all - I won an ebay bid and bought a yzf450 quad. I'm used to the performance as I have been using the same engine in mx bikes. Its an awesome ride, its been geared up and its not as aggressive as I thought. Wicked!