I thought that I should post my Hawk for sale ad with a review and rundown of the Hawk and its nature. There are lots of other reviews worth checking out, but figured I'd put out my two cents worth.
I have owned two Hawks, the second now being the one for sale. 1988 in blue and 1991 in red, the first and last years of production.
Let's start with some bullet points.
The gas tank mount is horrible and some of the essential rubber bits are no longer available. That said, it mounts the tank securely, but the rubber bumpers underneath the tank always fall off and it's a pain to get lined up and to take on and off. I think the design looks nice, but I'd add an average of ten minutes to your estimate every time you need to take the tank off and put it back on. Sometimes it'll be smooth, othertimes it'll be a real pain. No other bike seems to have the same forward lip and collar setup.
The hip and knee angles are rather tight if you're around 6' tall (of course inseams vary). On my first Hawk, it was quite cramped for me. On my second, I started to get used to it and now it's completely fine. The first time my Dad sat on my second Hawk, his hip cramped up. The Hawk may not work for you at all if you're tall, even if you want it to. That said, it's been okay for me at 6'1" and anything between 230 and 255 pounds.
The gas tank is small, so the range is quite low. I think the most I've filled up at was about 88 miles and that was running on reserve for a while. Some people do fit bigger tanks with some success (Honda F2?), and there's a goregous 5 gallon carbon fiber tank. The stock takes 2.5 gallons if I'm not mistaken, but in reality I fill up about 1.8 gallons.
Front valves are a real pain to get to. The thermostat placement seems like a complete afterthought.
The single sided swingarm has a rather complicated eccentric setup. The bearings are more expensive and it can get tight and hard to turn. The single sided swingarm looks cool, but two sided swingarms are probably a better bet from almost every perspective except styling (for a chain driven bike).
New parts availability is not very good. Honda in general made a lot of bikes for a few model years and did not produce many parts. A lot of essential parts (like the fuel pump) have to be bought Chinese, overpaid on ebay, or cross referenced. The fuel pump might take you 30 minutes to find and guess at a good compatible one.
The bike is harder than it needs to be to work on. 4 spark plugs for 2 cylinders, vertically split engine cases, single sided swingarm arrangement, fuel pump, annoying gas tank, limited front cylinder access.
No wind protection. Even a little bit can make highway riding bareable.
Stock gearing is has even toothed sprockets on both ends. This contributes to uneven wear which will make you replace it sooner. Easy improvement is a 43 or 41 tooth in the rear.
Suspension travel is a bit short and overdamped. Not the most comfortable bike to ride on most roads.
The front wheel is 2.5" wide which is a half inch too short for proper fitment of any radials. That said, a shallow profiled 110/70-17 seems to work fine, like the Bridgestone T30 EVO. If this was a 3" or 3.5" wheel, it'd greatly improve tire choices.
Airbox is tough to get on and often ends up cracked, with only cracked replacements on ebay.
Lower / mid range is rather weak, bike likes to be reved. It's like an inline 4 that way, but with a lower redline. Not a torque monster at all, just has a little more torque than some other bikes.
Cheesy plastic headlight cover gets yellowed over time. Lighter weight, though.
For the displacement, doesn't make a lot of power. It's enough for most, just not a lot for a 647cc.
It has a centerstand! It also has grabrails that double as tie down points. Very handy.
Nifty sidestand has a rubber extension and snaps back up when you forget to pull it up (in theory, anyway). Main perk is that there's no side stand switch to deal with.
Lovely handling when even partly dialed in. Great mass centralization.
Wonderful sound, even a bit of gear noise.
It looks fantastic. I know this is subjective, but it's pretty much a fact for me.
Build and finish quality overall quite good.
Brakes have good feel and are sufficiently strong just setup correctly.
Excellent low speed balance for a bike in its class. Has at least a bit of steering lock to make tight parking easier.
Tubeless tires. A godsend from the Heavens above.
Motor seems to have good longevity when taken care of.
Fantastic bike in the twisties.
Good forum and aftermarket community (hawkgtforum.com, hordpower.com)
Narrow tank and grip with the knees makes it a phenomenal form factor if you like narrow bikes. Though I prefer an inline 4 for this sort of bike, the V-twin gets you a fantastically narrow bike. So I'd say with some hesitation that I like the behavior of an inline 4 but the handling of a V-twin.
For me, what kills this bike is the mix of exotic traits, limited parts availability, and difficulty fabricating the parts that aren't available. It's a bit of a pain to work on and it's biggest redeeming trait is its handling.
I think the Hawk either needs to go into the simpler camp (easier to work on, 2 spark plugs, two sided swingarm) or be pushed into the exotic, racing camp. I had an FZR-400 once and though it was a real pain to work on, its sublime performance made it worthwhile. You knew you were working on a race bike so it wasn't a chore. The Hawk though, isn't nearly a race bike. It can be made to be competent. The engine is overrated and the handling is good but will never be wonderful at speed without a frame mounted fairing. So it's maybe 90% as hard to work on as an FZR-400 without the performance to make up for it. Though the Hawk has more steering lock than the FZR (still not as much as I'd like, could use another 10 degrees).
To give a quick story on why the parts availability and "exotic" traits of the bike are an issue, I decided to have the petcock rebuilt on my second Hawk. Reserve would leak through the face of the valve. Well, the petcock isn't rebuildable. What this means is that there's no official kit for it and the face is riveted on instead of screwed on. However, the Internet tells me a part number for a replacement rubber that'll work, and of course the rivets can be drilled and tapped. No big deal, right? Well, the rubber bit I got was too small though it seemed like it might work at first. Got home and sure enough, leaking much worse than before with no way to stop it. I just had to let the bike let out gas while I ordered a petcock for it.
After we replaced the petcock, the fuel pump started going out (never stopped pumping, even after it had pressure). The fuel pump isn't necessary on a bike like this, they could've messed with the airbox and tank to put it in a purely gravity fed setup. So, looked for a fuel pump as they can be tricky t rebuild and don't have kits. The factory one was no longer available, so had to spend quite a while looking for a comparable Japanese one. I did find it and it worked fine, but it was time spent that really didn't need to be spent -- for a bike of this nature. You could have a 400-something pound bike making 40hp at the wheel, with good handling traits, short wheelbase, etc, all that's easy to work on and without these silly, needless bits.
So the bike doesn't physically fit some taller riders, the carrying capacity is not all that high, the range is low, the motor is adequte, and the handling is good.
But, it is a lot of fun to ride. In general on a classic bike you either need to be able to make parts or buy parts for it to be economical. If you're making parts, it should be for a simpler build which this is not. And in this case, many aren't available. Though, the aftermarket community is quite good and there are forums for them.
It is a fantastic bike around town and in the twisties but that is about all. If it were easy to work on and had parts, it'd be a great all around daily rider (mostly for shorter riders). Not a tourer, but that's okay, can be another class of bike altogether.
If now you're not interested in a Hawk, watching a few videos of them may change your mind about everything I've said. The sound is fantastic. And in their element they are very special, even if beaten by other bikes in similar classes.
If the maintenance cost is not a concern to you and you're willing to pay more for a nice looking and unique bike, it does make a fine bike for commuting (not on the interstate), twisties, and around town. I just think there are better values for bikes with similar traits.
Here's a video on my first Hawk, recorded with an iPhone ducttaped to my jacket: https://www.youtube.com/watch?v=l8cTzvhz0MA