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I own a Hero Honda CBZXtreme bike. The top speed that I have reached is 122Km/Hr. But I am not able to reach this speed always. Sometimes the speed does not even cross 105 Km/Hr while travelling on the same road. Whats the catch here? On what does the top speed depend?
I don't seem to understand this. Because I am using the same bike and the same road every day. But the top speed differs daily.Does it depend upon how and when I shift the gears or something like that?

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You'll find the following will all affect your speed and acceleration:

  • wind speed - a head wind will slow you down more than you would think
  • your clothing - this directly impacts drag
  • bike configuration - you'll go slower with panniers on than with them off
  • weight - a full tank will mean you accelerate more slowly
  • temperature - cooler air can give you a better top speed
  • what type of fuel - if tuned for it, an engine can get a higher speed on better petrol
  • how warm the engine is - many engines will not produce full power until warmed up, and engines that are too hot will also underperform (see temperature) so cooling is essential at high rpm
  • type of tyre - some have higher rolling resistance than others
  • air pressure/oxygen content - engines are more efficient at sea level than up a mountain
  • exit from previous corner - if you come out of the previous corner faster, you can get up to speed faster
  • gear choice - a lower gear has more torque, but a lower top speed, so changing up early will lead to a slower acceleration (known as short-shifting)

So see which of these have changed between your different attempts.

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  • "how warm the engine is" and "gear choice" interest me. can please explain in detail how these affect the speed and what I should do to maximumize the speed?
    – Ashwin
    Commented Jun 1, 2012 at 8:22
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    You want your bike to idle at 3k RPM? That's a big waste of fuel. Mine will rev in that range while the choke is active, which it should not be once you're up to temperature. The other adjustment is an throttle idle stop where you can set this, but again - you should probably set your idle more betweek 1k and 1.5k.
    – Ehryk
    Commented Jun 1, 2012 at 9:51
  • @Ehryk : okay..so its normal for the engine to idle at 1.5k rpm? I thought this was the problem for my bike not reaching the top speed nowadays. Then what can be the problem for the bike to not to respond to throttle as much as it should(when I up the throttle to maximum, the bike does not seem to respond to it)?
    – Ashwin
    Commented Jun 2, 2012 at 4:05
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    I would either clean your carburetor yourself or have it cleaned, for a start. I also put in small fuel filters in my bikes to prevent particulates from getting into the carb from the fuel tank.
    – Ehryk
    Commented Jun 2, 2012 at 4:30

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