Can someone explain ENGINE POWER BAND to me?

My KZ750 (twin) REALLY kicks in around 6-8k RPM. Same with my Honda and Yamaha. Scientifically, why is there such a BOOST at high RPM for certain bikes?

My 77 KZ750 Twin is a TURTLE until I hit 7K and then it turns into a different bike!

Think about it this way, if you're tooling around in a parking lot or stuck in traffic, would you want full power?
Bossie's like a kitten at low RPM's but gets MEAN when I drop down and grab a handful at higher RPM's. I love the wide eyes and open mouths on the cruiser riders when she "Comes on the cams." :woohoo:
Steve

SWest wrote: Think about it this way, if you're tooling around in a parking lot or stuck in traffic, would you want full power?
Bossie's like a kitten at low RPM's but gets MEAN when I drop down and grab a handful at higher RPM's. I love the wide eyes and open mouths on the cruiser riders when she "Comes on the cams." :woohoo:
Steve

This is exactly what happened when I was riding with my friend, he on his Harley, me on my KZ750. Once I hit 70MPH the bike took off. He was shocked. I can only image what the 4 cylinder KZ750's can do.

:lol: :lol: :lol: Try a 1000. :woohoo:
Steve

If it's a dog at low rpm you can try smaller carbs, shorter gearing or advancing the timing. All will affect top speed. It's give and take tuning.

Golly Dude, I don't get that at all. I have two 750 twins and they pull strong down low and kind of run out of breath at the top end. I turned one of them into a trike because of their reputation as a good bike to pull a sidecar.


Power bands are described as either peaky or flat. A bike with a peaky powerband will not be very impressive until you get it to that one narrow RPM range where it makes all it's power. Conversely a bike with a flat powerband is easier to ride because there is power, albeit less of it, at all RPMs.
Bill

650Dude wrote: Scientifically, why is there such a BOOST at high RPM for certain bikes?

Power band is usually a term used for the characteristics of a 2 stroke which refers to the range of RPM's that the engine produces peak power and is running probably at it's most efficient .
Most 2 strokes have a step up in power when they come on song and the band of rpms this occurs is called the power band.
Port timing overlap is the main governor and because a 2 stroke has twice as many firing intervals as a 4 stroke the power increase is more noticeable when it comes in.
A wide power band is the result of less overlap and will be smoother, more progressive and suited to road riding.
A narrow power band will be the result of more overlap and more suited to competition.
In a 4 stroke the power is generally more linear and stable due to the torque produced from a 4 stroke engine and the power is seen as more of a steady curve with less of a jump coming on and off the power.
Like a 2 stroke , timing overlap will alter the power characteristics with lower (narrow) camshaft LC numbers pushing the power up the rpms and higher (wider) numbers bringing it down.
Depending on their cam timing, compression ratio (state of tune) etc certain bikes will have that "boost" at higher rpms than others.
If your 750 twin appears to be behaving differently to others maybe it has altered cam timing or other modifications to boost the top end performance.
This will have the trade off of losing some bottom end power in the process.