I've never ridden a bike there but I was in DVNP 2 years ago at that time (mid-late March) with a 4x4 group and here's what I can pass on:
1. The gas stations at Scotty's Castle and Grapevine/Mequite Springs will be closed, so plan accordingly.
2. The road between Ubehebe Crater and Teakettle junction was the WORST washboard road I have ever driven on, period. It took us around 2 hours to go the 20 miles. On our way up there, we ran into a couple of women in a late-model Suburban who had driven from Teakettle to Ubehebe without airing down their tires. They experienced 3 flat tires and were only able to keep going by driving a little, then stopping to air the tire back up, and then driving some more.
3. Be prepared for extremes if wind and cold near the Racetrack. I don't know if you're going to camp out or if you're doing the trip all in one day, but we camped out near Teakettle Junction and the temp dropped to about 28, and the wind was whipping around with gusts of 25 - 50mph.
We didn't do Lippincott or Hunter Mountain so I can't comment on those trails. We did do Mengel Pass and Goler Canyon, from East to West and they were both pretty decent. I think it helped that we were heading downhill on the worst part of Goler.
Martin (AKA ZappBranigan)
"Branigan's Law is like Branigan's Love: Hard, and Fast!"
Current Ride: 2002 BMW R1150R