In the UK, when you pass your bike test (oh , this is complicated so I’ll just make it simple but there are exceptions of sorts to these rules) you will usually be restricted to riding a machine with 33bhp for two years, after that you can ride anything on full power.
The result is that there is a small market for 33bhp machines, and a much larger one for bikes that take to restriction well.
There are three main ways bikes are restricted in power (there are other ways that the Japanese restrict machines on speed rather than power)
One, mechanical restrictions of the throttle controls, such as cable sleeves, stops in the throttle lever restricting rotation, stops within the carbs preventing full movement of the sliders.
Two, air intake restriction, in carburettors this is done by putting in what is effectively a large washer in the carb inlet or some makers use rubber inlet port cut outs, remove them and you have full power(well - not really but I’ll explain).
This method is at present the most common, but the jets must also be changed as the mixture would run too rich, so simply removing the air restictors could lead to problems. It is not unusual for individuals to buy a full power machine, get it restricted, and obtain the legally required power output graph, and then take the restrictors out.
When you take a bike in to be restricted this way, the dealer is not allowed to give you the original jets back until he sees your licence has had two years bike time on it.
Electronic, reprogramming of the engine management system, its not all that common simply because new riders are not in the habit of buying brand new machine that have such system, these being reserved for more expensive and sophisitcate machines.
Some machines can be restricted by using more than one of these methods, for instance, the Suzuki GSX1300R Hayabusa has electronic limiting, along with a stop on the handlebar throttle control, though quite why one would want to own such a severly castrated machine is a good question, since you would be suffering all the depreciation and getting none of that 196 mph amusement.
Not all machines take well to restriction, even when it can be done.
Restriction tends to be most noticeable when you open up the throttle to accelarate, such as overtaking, its the torque you lose, not so much the speed.
I have not personally seen any machine above 750 that has been restricted, no surprise to me, but it seems that even sports bikes of 600cc don’t really take to it all that well, somehow the handling in corners is just not as sure footed.
The best bikes that I have seen for restriction are things like the Suzuki GSF Bandit, Hondas Nighthawk CB750, they tend mostly to be conventional road machines that don’t need to be revved hard to get access to their performance.
I don’t know about restricting cruisers, I could make a guess but in all probability I would be wrong, I would be interested in knowing how well such bikes take to it.
My guess is that cruisers don’t make all that much power anyway, not when in original condition, and that restriction probably only takes a little away from accelaration and to get access to the (slightly) higher power you have to rev into a range where the vibration is intrusive so that restriction doesn’t really make itself felt all that much, as revs are not what these bikes are about.