AFAIK = as far as I know.
The bike my buddy has was set up for MX and was raced frequently before it was retired and sat in some guy shed for a few years before it was given to my buddy. Yes, given. It was in shockingly good shape when we picked it up. He had hinted at passing it on to me since he was running an older KTM 300 at the time, but the YZ was in much better shape than his current ride so he kept it. Fork rebuild, top end, all bearings and bushings replaced, and it's a wicked machine.
The 41mm usd's were decidedly lackluster for MX use. Simply too spindly. But for trail riding they have proven to be pretty smooth. On his bike, the clicker settings on the rear shock along with preload on the rear spring seem to affect the front suspension greatly, so check that for sure. If there's any grab or sticky feeling when compressing the front the bushings will likely need to be checked/replaced. I've seen some info somewhere on those forks for shim stacks, I'll have to see if I can locate it again.
Here's my buddies bike before/after rebuild. I liked it better in purple/white personally, but he's a freak.... It's sporting yz125 plastics now, and a hacked up graphics kit from a blaster.
http://www.bikepics.com/members/factorfreejack/89yz250/