Hi there guys i was thinking of buying a new motocross bike but don't know what to buy. I am 28, 6,5 and weigh 247lb's (don't laugh)

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I was either going to buy a RM 250 2002, which has had a lot of extra's and is going cheap, or a CR 250 2001 which has been well maintained and the 2000, and 2001 are the best years for CR, or last but not least a CRF 450 which i am still looking for to get for the right price. In your opinion what is best suited to my requirements? would the suspension take my weight?
I know that the 4 strokes are dearer to buy and cost more to maintain then the 2 stroke but would it be worth it in the long run.
All your opinions would be very much appreciated as i am fairly new to motor cross.
Thanks. Martin