To a first approximation, engines of the same displacement make about the same torque, whether they are singles or multi-cylinders. That being so, engines of the same displacement ought to turn about the same rpm to make the same horsepower. The required horsepower is about the same for any motorcycle running the same speed. That would tend to make me think motorcycles of similar displacements should be turning roughly the same rpm at the same speeds.

Motorcycles with bigger displacement engines make more torque. Horsepower is the product of torque and rpm, so to make the required highway horsepower they can be geared to turn slower.

An old rule of thumb says an engine, breathing well, will make about a ft-lb of torque per cubic inch of displacement. The S40, as its name indicates, is a 40 inch engine. The literature I have seen shows about 30 ft-lb of torque, which isn't too spectacular. True, there is a percentage loss from crankshaft to rear wheel, usually estimated at about 15%. Even so, the S40 ends up a little on the low side. And its torque curve isn't very wide, either. It only runs from maybe 3000 to maybe 4500, with the peak about 3700 - about 55 mph. The long stroke limits its top rpm to about 7200, and the rev limiter cuts off at 6500 according to the reports. It is also a little inflexible, in that it will not pull cleanly below about 35 mph in high gear, probably about 2400 rpm. I know it is easy enough to downshift. But the much-higher revving engine in my 250 Ninja WILL pull out from 25 mph in high gear, then go on to outrun the S40 easily.

I was using for reference the torque curve published in the Motorcycle Consumer News issue of September 1996. The lowest number shown on their curve is at 2500, and is 12 ft-lb. It is 22 ft-lb at 3K; 30 at 3500 and 4K, down to 25 at 5K (the highest shown and also the horsepower peak at 24.6 hp). The lowest shown number is fairly often the lowest RPM at which the engine will run at wide-open throttle. Their numbers, like most magazine reports, are rear-wheel measurements probably made on a Dynojet.

My S40 will also pull out from 30 mph in high gear, and as you say one can clearly feel the power pulses. I know that, but I use as an indicator the feeling of drive-line play. The belt absorbs some of that, especially since there is very little backlash in the belt itself. When the engine rpm gets too low one can feel (and hear, with a quiet muffler) the backlash in the drive train.

You are correct - the 250 Ninja is a much more "tweaked" engine. Its highest torque is said to be up around 11000 rpm. Many magazine reviews claim it has to be revved up to 4K or so before it will leave a stop light. At least on mine, that is untrue. Although it does not have a really strong low end torque, it doesn't require that sort of revving and it is tractable enough that it can make ninety-degree turns on ordinary city streets without downshifting. The S40 will not do that. I would also add that the 250 Ninja costs about a thousand dollars less than the S40.

There was an interesting article published a few months ago in one of the motorcycle magazines, probably Cycle World. I cannot reference it because I donate my Cycle World magazines. It referred to the history of the Dynojet and the Yamaha V-Max. Apparently, when the V-max came out one was tested on a very accurate water-brake dynamometer, and produced a pretty impressive horsepower. The engineers designing the Dynojet were sure their unit was accurate, but for some reason the showroom V-Max they tested produced a lot less horsepower as measured on the prototype Dynojet. The software in the Dynojet was "adjusted" to make the numbers jibe better, since no one seemed willing to admit Yamaha might have slipped a ringer in for the original testing. Ever since, it is said, Dynojets read more horsepower than is really there.

You also commented on tweaking the Savage/S40 engine. Sure, it should have been done at the factory. But that would likely have made the motorcycle more costly and thus destroyed one of its appealing features. And I point out that aftermarket modifications, if they increase either exhaust or noise emissions, are illegal under Federal law. It can be modified, BUT NOT LEGALLY.