Josh, seriously, Vegas is a very challenging location to find a 'good ' route to and from. It's too far south, and too deep in the desert (read: 'boring') to be ideal. So, if I HAD to go to Vegas, I'd fly! But, if I HAD to ride to Vegas, mid May, here's a couple thoughts:
* the coast is nice, as a way of getting south, but May is still frikkin cold out there. write that one off.
* the back-side of the mountains is drier and warmer, but 97 and 395 and 95 are amongst the drone-iest roads in western North America, so unless you trade in your Zee for Harley, I'd recommend elsewhere.
* so that leaves a) mid-land and b) inland. one down; the other back!
day 1: I say, fuck Washington, you can ride that anytime, so bolt south on I-5 to the Oregon border. then jog west to Clatskanie and have a blast down 47, etc to Eugene. one day, 820 kms, 10 hrs. logging, then wine country. very pleasant. Eugene is a nice town, lotsa fine eateries, college town, so lively.
https://www.google.ca/maps/dir/Vanc...94a43894d!2m2!1d-123.0867536!2d44.0520691!3e0
day 2: ride the best parts of I-5 and enjoy it. then bugger off into the wilderness.... O-Brien ( fuel) to Happy Camp is totally remote, ridiculously twisty. 96 flows. Scott River Rd is more of the Happy-Camp-ishness but narrower and twistier. CA 3 is an absolute gem! wild, tight, and fast. the Hayfork cutoff will have you laughing out loud in your helmet. and you finish with arguably the best bits of 36...
775 kms 11hrs - a BIG day! (p.s. ignore the weird google map jog left north of Happy Camp )
https://www.google.ca/maps/dir/Euge...e8736765a!2m2!1d-122.2358302!2d40.1784886!3e0
day 3: tough! the best riding is west of the Sierras, but you gotta get across one of the passes. and it's early in the season. these are 8000 and 9000 ft passes, not 5000 ft like the North Cascades, so weather is chancey. and the higher passes may be closed and/or snowed up.
(drinkin wine and thinkin.... I'll post more as it comes to me...)
how 'bout this: Feather River to Quincy: fast, fast, fast, and superb. La Porte Rd ( Race Track in the Sky). Downieville. south to Monitor Pass (CA DH #1). Ebbetts Pass (maybe open, maybe not). overnite in Sonora - Rodeway Inn, right downtown. eat at Diamondback Grill - excellent!
860 kms 11 1/2 hrs - full on day! you're gettin' weary by now!
https://www.google.ca/maps/dir/Red+...676254777!2m2!1d-120.3821724!2d37.9829496!3e0
day 4: can't be done! 1050 kms 13 hrs. south along the Sierras. out thru Death Valley. LV.
https://www.google.ca/maps/dir/Sono...6d5b379a3!2m2!1d-115.1398296!2d36.1699412!3e0
the route's OK, it's just the distances are too big... I think so anyway... push on a bit each day, and get to Oakhurst 3rd nite and it might work... (Oakhurst Lodge recommended; Di Cicco's across the back serves great Italian food) or eliminate some of the earlier stuff and get to say Three Rivers CA 3rd nite and you'd be OK. apparently Comfort Inn is the spot there, and the Mexican diner across the street comes recommended. ( thank you Tim Mayhew at pashnit.com tours)