When I was a kid there was a motorcycle shop quite aways from me. My friends and I would go there occasionally to look at the bikes. This was the early 70's. One bike always stood out, one that I always liked the most. It was a 500cc single cyclinder cruiser. I don't remember if it was a yamaha or a suzuki. The dealer sold both brands. I always wanted one. 40 years later I bought a single cylinder 650 Savage, because I liked it. It does not run currently, stripped threads in the head that need repair. I bought the bike because I like it. Does it go fast? No. Does it accelerate fast? NO. Does it stop fast? No. Comfortable? No. All these negatives and the bike still appeals to me. The bike does'nt fit me, my friends say I look funny on it, even laugh a little, at me. I still drive it, like it and enjoy it.

My Nephew has a Ninja 250r that I have not gotten a chance to drive. It has 26.4 hp at the rear wheel at 11,000 rpm.
15.58 sec at 81.98 mph in the quarter mile.
maximum torque is 13.6 ftlbs at 9750 rpm.

The Savage has 30 hp, or 31 hp at 5400 rpm. I don't know if that is measured at the rear wheel. So it should have more acceleration with the same mass as the Ninja. It would certainly have more torque, it runs with half the rpm. The Savage engine is 2.6 times larger that the Ninja's engine.

Will the Savage out perform the Ninja? I doubt it, maybe the first few feet. It is not designed to launch, the riding position is not so good on the Savage. Aerodynamics are horrible on a cruiser. The Ninja designers have implemented some aerodynamic improvements on the Ninja. Better aerodynamics means that it takes less power to drive at all speeds except stopped. The Ninja probably presents a smaller frontal area, further decreasing the hp requirements.

Horsepower is meaningless? It is not a measurement?
It certainly is a calculation, and we certainly do measure it. We measure the force, the distance, and the time and that gives us power.

Torque is also not meaningless. We measure it, calculate its value and use it to determine the required strength of the crankshaft, more torque, larger crankshaft, and then we recalculate the torque at each stage of the drive system to properly size the components of the entire drive assembly. Torque values are not used to calculate acceleration.

Tractors have massive rear wheel torque numbers. That does not equate to acceleration. They have large torque numbers at the crankshaft. If I am going to the dragstrip I am not going to use a supercharged tractor motor and win any races.

Funny cars have large torque, power, and  rpm values. They spin that motor as fast as they can. The volume of the cylinders are maximized. Camshafts are designed to optimize the intake of energy at the highest rpm's possible. To further increase the energy intake of the engine they pressurize the the fuel air mixture to push even more energy into each cylinder every cycle.. and then use the higest compression that is possible. Say a little prayer before they launch I imagine.

Can the performance of the Savage be increased? Yes. Not the best platform, but yea.

Of all street bikes that I have driven, the Savage has the poorest overall performance. If you are looking for perfomance, you purchased the wrong bike. You buy a Savage because you like it.

The 250 Ninja and the S40 are an interesting comparison - and I happen to have both. Both have about the same horsepower, around 25 or so. Their weights are similar, about 395 for the S40 and about 350 for the Ninja. The S40, according to published reports, is faster 0-60 mph. But the Ninja has a higher top end, usually reported at 95-100 mph against the S40 in the 85 mph range.

As a rough rule, naturally aspirated engines will produce about one ft-lb of torque for each cubic inch of displacement. The Ninja displaces 15 inches, and produces around 13 ft-lbs. The S40 displaces 40 inches and produces around 30 to 35 ft-lbs, so both are in the range where they would be expected to be. At highway speed (say 60 mph) the Ninja turns about 7500 rpm; the S40 about 4000. The difference in torque is compensated for by the difference in gearing, so the torque at the rear wheel (and thus the ground thrust) is about equal. As it happens, the fuel consumption in mpg is similar, implying production of about equal power.

In actual riding, there are lots of differences aside from the riding position and suspension. From a stop the S40 has to be treated gingerly on gravel roads lest it spin the wheel. In town the Ninja can take right-angle street turns in high gear, while the S40 lurches unless downshifted to perhaps third. Once at highway speed the Ninja's acceleration feels considerably more effortless than the S40, in any appropriate gear.

Those are my observations, based on my experience with my own bikes. Your experiences may differ.