lots of posts on lots of bikes that supposedly are sleepers. I tend to be much more critical of what constitutes a sleeper bike. Bikes have been fast since they were invented, and most of the public knows that. A sleeper bike can't just be fast, it has to be very fast.
For me there are two parts that make up a sleeper bike. First, a sleeper bike has to be as fast as current sportbikes, and pretty much faster than the 600's. With that in mind, i'd consider a sub 11 second 1/4 mile a good performance measure to meet. A sleeper bike should simply be faster than most motorcycles out there. And for the second part, the type or style should not have a history of being fast, otherwise it's not a sleeper. With that criteria there isn't much to choose from, but frankly the list for sleeper bikes should be short, otherwise everything is a sleeper bike. So for me, naked (aka std) bikes, touring bikes and even harleys (haha) are not sleeper bikes.
Naked bikes in the early days were the sport bikes of the time. And even after fairing bikes were developed there have been a lot of very fast naked std bikes available. Not a sleeper.
Touring bikes have always been fast, at least compared to cars. Nothing new here or to write home about. They have always been and are generally faster than many mid-displacement bikes. Fast but not super fast. Not a sleeper.
Harley's and custom choppers have always been fast compared to cars too. Even if slow compared to many bikes, many are modified to bring about more notable speed. A fair amount of super fast heavily modified examples are out there. Not a sleeper bike.
A slow sportbike is not a sleeper as i mentioned in an earlier post. It is just that, a slow sportbike.
For me, one type of standout sleeper bike are the relatively new crop of fast adventure bikes that have come onto the scene. The traditional offerings in that type have forever been known to be much slower and lower hp, with a utilitarian off-road look that is far from exuding a sense of fast street performance. And it is only relatively recently that fast examples have been produced. There are some obvious new specific adv bike examples where the manufacturer has put a monster sportbike engine in an adv framed bike. Even if the bike is heavy 150+ hp easily overcomes that. A sleeper to the public big time. Interestingly there are a few middleweight engines out there in adv bikes that still do sub 11 second 1/4 miles because of a great motor, but also light weight. Those are the biggest sleepers imo because they are surprising to both the public and to many riders.
A scooter could be a sleeper bike, but even heavily modified, you just don't see real life examples out here. So no bueno for me.
As for a rider giving a bike sleeper status, yes, but that's about the rider, not the bike. I'd assume we all know that it is 90% rider on a motorcycle. I focused on the bike here in this discussion since the thread title is sleeper bikes.