I read the Indiana order in detail and motorcycling is not mentioned. It does mentioned that outdoor activity is encouraged as long as you maintain social distancing, and it did specifically mention bicycling is fine.
There is something to the idea that you don't want to occupy emergency services if you have an accident. However, I've been hit by cars twice while bicycling and twice while motorcycling; there's an element of risk to anything you do. Heck, if you lie in bed long enough with the covers over your head, you're going to need an ambulance sooner or later. So if you manage risks, I don't think motorcycling is necessarily "selfish", or outside the scope of prudence.
And if you think through the practical side of things, the cops aren't pulling people over at random and there aren't checkpoints where they're checking your papers; there aren't any "papers" to check, and there aren't enough cops to do this anyway.
So yeah, I went for a nice little ride yesterday. I did stop by a grocery store to grab a few things I needed (I was on my V-Strom, which has hard bags; that's how I normally do my grocery shopping most of the year), so I suppose I'd at least have an excuse if questioned by jackbooted thugs. I didn't see any jackbooted thugs, and the police I did see didn't give me a second glance.
So here's where I land on this. YMMV, of course; as mentioned some places do specifically mention motorcycling. But I don't think they care about the riding; they mostly need people to skip the gathering and socializing motorcyclists are prone to.
I think the following is compatible with the letter and spirit of the order, at least here in Indiana. YMMV, and I am not a lawyer, only a reasonably competent human being with a decent level of reading comprehension. Heck, this might get me tasered or ticketed.
- Riding for allowed purposes ("essential" work, groceries, etc.) is fine as long as risk factors are managed.
- If they intended to ban recreational motorcycle riding hereabouts, they would have done so; the Indiana order is ten pages and it is quite thorough in every other respect. The do mention that bicycling is OK, and motorcycling does have some things in common with that.
- Recreational day rides are perfectly compatible with the concepts of social distancing and limiting virus transmission. You'll need to work out ahead of time how you're going to clean your hands during and after gas stops, and be prepared for closed bathrooms. (With pay-at-the-pump, pee-in-the-woods, and carry-your-own-drinks-and-snacks, you could go quite some time without getting anywhere near any other humans

...)
- No groups or pals or gatherings. In JohnnyL's case, he and his son are in the same household already, so it's perfectly fine for them to be near one another. And it's a nice bit of added safety.
- Dry and sunny only. You obviously want to manage risk to the highest degree possible to avoid occupying EMS, so for the duration I won't ride if there are additional risk factors like rain or darkness. On the plus side, there's a lot less traffic, which is the main hazard to motorcyclists.
- I also limit the distance. If I'm a carrier, I don't want to spread this to some tiny town in southern Indiana. A normal day ride for me is 300-450 miles total, but for the time being I'm limiting my rides to a fairly small radius of 25 miles or so.
- Manage risks more conservatively than usual, if possible.
- Spend some extra time ensuring your machine is mechanically in perfect condition.
- Think about how you might manage things if you have a breakdown. Limiting ride distance is part of this.
- ATGATT, of course. But that goes without saying any time.
- I haven't heard of nor do I expect to hear of any targeted enforcement, but I suppose it couldn't hurt to have an excuse at hand... a backpack or bags with which to carry groceries.
- I'll also point out that there is also increased risk in NOT riding; skills deteriorate over time. Here in Indy, the climate is such that we usually get some just-warm-enough days in every month and I make a point of getting out for rides to maintain skills; still, it takes some time every spring to get sharp again.