It is a toss up... if I try and go in April good chance of hitting snow in the CO mountains. Too late in June is hot. End of May and 1st part of June it is hit or miss.
I have vented as well as heated gear, but no snow tires for the bike.
I work a rotating schedule as well, so have to pick times on my off days.
We did 191 last year late May and it was perfect.
Worse case may be a little warm around Flagstaff and GC, but it is still high desert and not Phoenix....