It is somewhat easier to get higher volumetric efficiency from a smaller cylinder and to get it to rev higher, but there is also total weight of the engine and the biggie, the internal friction caused by having more cylinders. The early 500 fours made 36whp, about the same as a decent (and much lighter) 400 single, and you can guess as to which is faster.Originally Posted by cnk
The main contributors to tourque curves are not the number of cylinders a machine has. A single can be quite peaky if the cam timing and lift are tuned for it. A 50hp 500cc single will have a substancially similar powerband to a 50hp 500cc twin provided similar head and cam designs, with the single having an edge in traction because of the widely spaced power pulses. The single will also be lighter, have less gyroscopic resistance to leaning and less wind resistance. The thing is, you can get a 500 twin to make 80hp, while the single will be limited to about 60hp or less. Something to do with more valve area and higher redline.
In cars adding cylinders is done mainly add displacement while keeping combustion chamber size small enough to avoid detonation rather than to increase redline, with the nearly agricultural redlines of auto engines.
The main drawback of the EX500 is its dated head and fuel system design. When it was first put into production in 1986, the overall power to weight ratio of the bike was slightly higher than the 600 fours of the day, with the exception being the 600 Ninja. All these years later it still makes 51 wheel hp while the 600's have gone from 70ish to 100ish and have gotten lighter than the 500 twin. Aprillia has just started producing a modern 450 twin which produced over 80hp in race trim, and will likely lose just a little of that edge for street use; think 70hp.
The EX500 was called a "finger in the light socket sportbike" with "astonishing" power when it was new, but I read a recent article where it was called so boring that no one should even buy it. Imagine when an STI, which has similar 1/4 mile times and similar handling (on pavement) will be called so dull that it wouldn't even merit a test drive, except as a first car for teenagers. This is in effect what has happened to the EX500. A real beginner bike is a light dirtbike that allows you to exceed the limits and still get up and ride. Try that on any streetbike and you will get punted to the moon. That leaves most street riders as a bunch of chicken sh** pussies who disgrace their mounts in front of porky cars. (Like in front of my 2.5 on the twisties)