Just for laughs, quickest 250cc dual sport, lol.

Discussion in 'Thumpers' started by fightinggoat, Aug 14, 2012.

  1. IheartmyNx

    IheartmyNx Ihave2draft

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    Yer telling me... 120/70, 60/45 and a 46/35 in the last month.

    Other than that it's been 3 years since my last "speeding" ticket... (They always come in 3's:lol3)


    ...
    #21
  2. perterra

    perterra -. --- .--. .

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    When did lingenfelter start racing 250 thumpers?
    #22
  3. fightinggoat

    fightinggoat Adventurer

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    Sorry, guys been too busy to look up all the specs and compare, if someone wants to gather up the info and post it then great, otherwise it will have to wait a little while longer.

    So, anyone have any comparison experience riding both a honda rebel and any of the 250cc dual sports?
    #23
  4. rpet

    rpet Awesometown

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    Generally we stay away from Rebels.
    #24
  5. mousitsas

    mousitsas Long timer

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    Assuming that it is not a single gear race, horsepower rules the game.
    Picture this.
    We have any bike with a super duper CV transmission box and we measure acceleration through the ratios. The race starts with the lower possible ratio in the CV box. The revs climb (ratio hasn't changed yet) till redline (max power point). During this sweep, max acceleration will be had at the revs of max torque since the engine force is greater at that point. However, after redline is reached, max possible acceleration is attained if we keep the motor at the max power point and change the ratios thereafter and not by keeping the motor at the max torque point.

    Moral of the story is that torque is good instantaneously and power is good on the long run. A 1/4 mile race (or any race) has to do with the 'long run'.
    #25
  6. IheartmyNx

    IheartmyNx Ihave2draft

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    I have a feeling you're looking at hp #'s and NOT the rpm they are generated at.


    Also, liquid cooling vs. air cooled are very different altogether despite what cc's they are.

    The Rebel for instance is air cooled and has two tiny pistons much like the liq. cooled Ninja 250 but not similar at all to a thumper.


    We can do this all day but it's useless if you keep going by hp #'s (which is higher?) but not the rpm's they are generated at.


    Compare a 4.3 Chevy to a 4.3 Ferrari... That might be a start for you. Both the same "size" but much different torque curves...

    You could even put the same compression and ignition FROM the Ferrari into the Chevy, but it still wouldn't make, or even come close to making the same power the Ferrari does.


    The new Turbo Cummins 6.7L only has a measly 350hp...

    Well how come the 6.2L in the SC Corvette has 638?

    Why not just put Corvette engines in the HD trucks? They have more power?
    #26
  7. davidb21

    davidb21 Adventurer

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    I took the msf course on a 250 rebel (not sure of year) and own a 2004 klr 250

    the rebel was WAY slower in acceleration
    #27
  8. ruppster

    ruppster Long timer

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    and swiping Carroll Shelby's quotes? (some give credit to Ferrari, but they likely ride Ducati) :rofl

    They're always related: hp=(torque*rpm)/5252
    #28
  9. michael1968

    michael1968 Long timer

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    The RPM at which the power is made is irrelevant when considering which bike is quickest. If you have two bikes of the same weight and torque but one has higher hp in a straight line race the higher hp bike will be faster (all other things being equal). The higher hp bike will rev higher (as shown by the equations/posts above) enabling the rider to stay in a lower gear for longer, that means that the engine can exert a greater force on the road over a longer time (which as is happens is the definition of power).

    As has been stated above, torque is important for in gear acceleration but that's not what this thread is about.

    You're point has nothing to do with this thread. The Corvette engine can rev higher to make more power. The truck engine is built for low end torque and super long service intervals.

    I know where you are comming from but the OP asked which bike is quickest, not which bike can I lug around all day without changing gears.
    #29
  10. HandKPhil

    HandKPhil Been here awhile

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    The answer of course is my 2003 KLR250. :D

    In all semi-seriousness though, I'd say the first year KLR250's, or the early XR250R's. Both were probably realistically making around 23-24 rwhp, and both weighed in around 290-300-ish, give or take 10lbs.

    My 2003 KLR250 really is pretty quick. I've re-jetted, drilled the top of the airbox, and installed an FMF Q4 can and UNI air filter. I've also installed a smaller countershaft sprocket. When I want to "make a statement" at a redlight, I rev it up to a steady 2300 rpm and let the clutch out "briskly" as the light turns green, and I usually cross about half the intersection with my front wheel about a foot off of the ground. This old bike has about 27,000 miles on her, and she seems to run better as she gets older :D
    #30
  11. HandKPhil

    HandKPhil Been here awhile

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    Dripping with raw power and speed....
    [​IMG]
    #31
  12. tjanson

    tjanson Adventurer

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    The early KLR250 (85-89ish) supposedly had 28 crank hp. That's the factory number....I wonder if it's for real though, because that's WR250R territory. The cams are the only thing different on the early KLRs. I have a '86 KLR250, seems quick but I haven't ridden anything else. It'll do 70 on the highway easy, and still have quite a bit of quickness left. I was thinking about getting it dynoed just to see what's up.

    Regarding torque and HP numbers as indications of performance... Peak HP and peak torque give you a general idea but tell you very little about acceleration. You need dyno graphs to really get a sense of a motor, oh, and while you're at it, the transmission ratios to see if it suits the motor's character. The best way to compare bikes is 1/4 mile times... but good luck finding 'em...

    If only we had a moto-Stig to run 1/4s on all the motorcycles out there...
    #32
  13. davidb21

    davidb21 Adventurer

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    i wouldn't be surprised if that hp number is right, not so many emission hurdles to get by in the 80's as now
    #33