Jimson, the swingarm is the original road bike one,theres no prob's with it.
The pipe is fine on a MX track, but have Vinduroed it and put a dent in the right header on a river crossing,like not bad enough to worry about.
No never weighed the motor, its lost a lot of its original weigh, counter balancer gone,magnto gone,starter motor gone. I did have a XT500 here once and to pick them up there didnt feel to much in it