I recently picked up a 92 XR250R with the 280 overbore, SuperTrapp exhaust, and WP suspension, front and rear. This motor really rips, loads of torque. Nothing like the stock XR250R. I can't imagine that it is as powerful as your 400, but for riding nasty, rocks and TIGHT woods, this is the perfect bike for me. I love it.
just for S & G's, I put the stock exhaust back on and lost a HUGE chunk of power.
btw, I am 6' and 190lbs.
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philb
my family:
92 XR280R
87 XR200R
85 XR100R