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Acceleration ideas anyone?

Discussion in 'Technical and Troubleshooting Torque' started by bilgola_boy, Oct 18, 2006.

  1. Got a chance to ride my first CBR250RR today, and after riding a Kawasaki Balius last week, it got me thinking? How quick are these bikes? The Balius apparently has the ZXR250 motor, and like the CBR, revs to 19,000rmp.
    I weigh about 70kgs, so how fast do you reckon these bikes are getting up to say 100kph? I didn't get a stretch of road long enough to test this, nor did I care at the time. But I am curious to see if anyone has done this test on either bike, and if you have an idea of how that time translates to someone of my weight :?: I'm a learner, so they felt like they had a bit of pace for a 250, but ballpark figures would be helpfull. :grin:

    Thanks everyone

  2. Most big bores 600 onwards will accelerate to 100 kmh in under 4 seconds (some of the hypersport litre bikes do it in just over 2 average acceleration being 3.5
    a 250 will range anywhere from 5-8 seconds depending on their gearing engineering etc.
    the cbrrrrrrrrr 250 is in the lower range.
  3. cbr will launch the 1/4 mile in about 14 seconds and hit 100 in around 5 seconds, ive ridden one, there pretty gutless low down until they hit about 10k rpm.
  4. Yeah my CBR 250 was as fast as my old car which was about 5 or 5.5 secs.
  5. And yes, the cbr is the fastest of the 250 4 stroke bunch if thats what you are interested in.
  6. But if you want the fastest LAMs bike, look at the RVF 400.
  7. jesus! just checked out them specs of that bike, nice! v4 goodness! sexy :cool: according to a few sites, it does 12 seconds down the 1/4 mile, damn good me says.
  8. Yeah and I heard one the other day with an aftermarket pipe and it sounded SWEET. :)

    I'm trying to get AMG to buy one for his first bike... the only thing is the price. About 8 - 9K for a 95 bike. :(
  9. :roll: Not really, it's got the same power output as any other post-94 4-cylinder 250 and the same government-limited top speed. The '85 Yamaha FZ250 predates the 40hp limit so has the same torque as a CBR but more power (45hp) and less weight. The Suzuki Bandit has the same power output and weight as the CBR, yet produces more torque. Really though there's not a lot of difference between 250s and they're all slow compared to larger bikes - so it's certainly not worth paying more than you should for a bike simply because of the perceived notion that it is the "quickest".
  10. Haha, are you serious? :p Just about ALL the 4-stroke 250's are the same as each other, around 40hp and the same weight. The CBR is slightly heavier than the ZXR250 as well, but if you put 55kg riders on them all there would be absolutley NOTHING in terms of performance difference.
  11. FFS people please use tiny url for long url's otherwise I'll bluecard the post and the link will be removed.
    copy the long url you want go to tinurl paste it in the click ok
    accept the new url and copy/paste it back in to this forum
    It takes an extra 30 secs but makes rading the forum much more pleasurable.
  12. on average if your not heavier than 90kgs, the cbr and zx2r will take roughly 5-5.5secs to hit 100. since you are 70kgs, with a good launch, you can hit maybe 4.5-5 secs to hit 100.
    as for the fastest 250 4 stroker in a straight line, the zxr is faster if you have 2 riders the same weight and skills. has more torque and has better top end power than cbr.
  13. Thanks for clearing that one up!
    Not after a bike because it's the "quickest" I was
    just wondering how quick they are compared to each other. I knew bikes where quick, but I thought it would be taking about 6.5-7secs for the 0-100kph dash. Well pleased to hear those times!
    It still asstounds me that you can - even as a learner- spend under $5000, and get a bike that will out accelerate a cage costing 10 times the price! Not quite as safe obviously, but a LOT more fun ;)
  14. /me kicks the long link square in the nuts - this thread is unreadable for me until it's fixed
  15. I suggest that any rider on a 250 that thinks they can get from 0-100 in under 5 seconds on stock gearing go get a reality check in the form of a stopwatch. If your really after nothing but acceleration on a 250cc bike then drop 2 teeth off the front sprocket.

    Its also worth mentioning that all of these power figures being quoted are practically irrelevant today given that most of these machines are now 15+ years old and have had their clocks wound more times than Victorian daylight savings. The only things that will determine if one bike is faster than another in the 250cc 4 stroke range is its state of tune, the gearing, the condition of the clutch, and the ability of the rider.
  16. {physics geekery}

    For a big bike doing a 3.5 s time for 0-100 km/h

    0-100 km/h = 0-27.8 m/s

    v = u + at
    27.8 = 0 + a(3.5)
    a = 27.8/3.5 = 7.94 m/s/s = 0.81g

    So the rider on a bike like that is experiencing 80% of the gravitational force downward on him/her as a forward force of acceleration (feels like a backward force as s/he clings onto the bike because every action force has a reaction force of equal magnitude in the opposite direction: seat pushes your arse forward, arse pushes the seat backward).

    Turn it around the other way to figure out how long 0-100 would take accelerating at 1.0 g = 9.81 m/s/s

    v = u + at
    27.8 = 0 + 9.8(t)
    t = 27.8/9.8 = 2.84 seconds

    So there are bikes out there accelerating at better than 1.0 g.

    {/physics geekery}