Hello. i was wondering if anyone that has a dhz 125, 140 or a 160 can get up to 120kmph.. from what my mates have told me.. myself being 60kg said its bull crap that the site say the 140 would do 120kmph. can any please let me know if this is true.. cheers!
Mine does a bee's dick/poofteenth of a shade over 120... but then it isnt really a DHZ, and it isnt really a standard 140...
^^^^^ describe what POWERBAND actually is and where it comes from...
every engine has a powerband and all engines are designed different so the powerband is different...(narrower or longer)
for the uneducated, ''powerband" merely describes the range of revs any particular motor has, between the minimum and maximum revs, that the engine makes it's strongest spread of power... once upon a time, four stroke motorcycle engines had very broad powerbands, ie they made power down low in the revs, through to high in the revs. (however, they *were* once low-revving engines.)
Old school two strokes were generally considered to have narrow powerbands, where the engine started making peak power high in the revs, until it stopped making power even higher in the rev range.
As technology advanced, four strokes became more peaky, with narrower power bands, and two strokes became less peaky, with broader powerbands. Expansion chambers (exhausts) on two strokes were better designed with the aid of computers and flow programs, to better aid the "supercharging" effect Cactus alluded to... and transfer ports had better flow designs, which means the transfer ports flowed better, and earlier in the rev range, broadening the available spread of power...
Powervalves were added to mx bikes in the early 80's to assist in spreading and smoothing the power delivery, basically they smoothed the transition where the gases flowing through the expansion chamber started to re-enter the transfer ports at velocity, by altering the exhaust port height, which altered the time, or rev range, at which the "supercharging" gases coming back into the motor started to take effect.. putting it simpler, pre-powervalve engines were peaky *****es with narrow power bands... powervalve equipped engines were smoother, with broader powerbands... riding the early pre-powervalve bikes was like being spanked on the back of the thighs unexpectedly with a steel ruler... you knew it was coming, but it always hurt anyway...
Modern Four strokes were lightened, cam profiles were changed, carbies that naturally produce power higher in the revs, strokes were shortened, flywheels lightened and their characteristics were altered to mimic the power delivery of a two stroke.. they became fast-revving, high-revving peaky engines, with far greater outright power, but lesser levels of torque, and that torque is made higher up in the revs...
Meaning a narrower powerband...
so over the years, the powerband of the two stroke mx engine, has become smoother and broader... like a four stroke...
the powerband of a four stroke has become narrower and more aggressive... like a two stroke...
if you still dont get it, the "powerband" is simply two words the wrong way round... it means "Band of Power"... but powerband sounds heaps more awesomer than "Range of revs in which your engine is making it's peak power Vs torque spread"....
im not finished, forgot the main character.
^^^ ha ha ha ha hah a
