I just got rid of my son's 01 CR50 S. I hated it! Good suspension. Crap motor! I went through many ignitions, three clutches, one crank, and one top end. The crank and top end got trashed after the first clutch implosion. The thing vibrated so much we constantly lost hardware and had to weld pipe & motor mounts, etc. BTW, I had the thing for sale for over a year. I lost my butt. :(
Since my boy will be 9 this month and he really doesn't care to race, we're going with a Honda XR80 (defines reliability). Change the oil, clean the filter and ride!