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Thread: How fast - on 50cc?!

  1. #31
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    In the mid-90s I did a little work with Rabasa Derbi in Catalunya, Spain. Like many of you, I did not really know this company beforehand. It seems they have a great GP history, but pretty much all with 50cc-250cc bikes, but really specialising in the smaller stuff. Barry Sheene started out racing small bikes with them, and their 50cc bikes really can fly.

    Many of your are surprised that a 50cc can hit the high speeds. But if you ride one you will see how they managed to accelerate slowly at speeds above 100k (which is why streamlining becomes so important), and how much of a (fun) effort it is to whip these bikes up to 100k in the first place.

    Even 50cc honda mopeds I used to ride with modified exhausts could crack 90k with a bit of a heads-down, but it was an experience I would hope not to repeat.

    As the yanks say, there's really no substitute for cubes.
    (metric version - more cc = more grin, Jim)

    For more on Derbi:
    "The 'Red Bullets' were a global success in the small cylinder categories for 40 years, collecting an incredible 81 Grand Prix victories in the 50, 80, 125 and 250cc classes, as well as 18 World titles. Ten individual crowns won by Angel Nieto (5), Jorge Martínez 'Aspar' (4) y Manuel 'Champi' Herreros (1) were added to by eight manufatcurers' titles, with two other legendary 500cc World Champions also having begun their careers with DERBI - the late Barry Sheene and, later, Alex Crivillé.

    DERBI returned to the 125cc class of the MotoGP World Championship in 1999 after an eight year absence. Within five years the factory have picked up 11 victories and finished runner-up in the championship on two occasions with Japanese rider Youichi Ui. During this time, DERBI has also left their mark on the championship with a series of technical innovations, such as being the first to use double front brake discs, as well as a winning spirit exclusive to the great factories and earned over four decades of effort and, above all, passion for motorcycle racing."
    Motorcycle songlist:
    Best blast soundtrack:Born to be wild (Steppenwolf)
    Best sunny ride: Runnin' down a dream (Tom Petty)
    Don't want to hear ...: Slip, slidin' away, Caught by the Fuzz or Bam Thwok!(Paul Simon/Supergrass/The Pixies)

  2. #32
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    6th December 2005 - 17:46
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    Aprilia Rs50,in the USA http://www.apriliausa.com/njb_dettaglio.asp?id=303
    Bonneville salt flats.160k+
    Stock derbi & Aprilia`s do 110kph (takes awhile)with eu3 mufflers and tiny carbs
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  3. #33
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    6th October 2005 - 21:45
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    Remember their 9hp is probably measured at the rear wheel. While your 26hp is probably measured at the crank with most of the engines ancilliries removed and then honda probably added a few for good measure anyway.

  4. #34
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    Quote Originally Posted by nudemetalz View Post
    I raced an RD-50 at about 1988-89. Clocked at 110-115km/h from memory. Weighed virtually nothing. It had a very peaky powerband and needed lots of clutch work out of corners

    Here's a couple of pics of it.
    That second shot is me on the sweeper onto the straight at Levels. I was nearly at maximum speed there, so you can imagine the poor wee engine pulling 12,000rpm all the way. I had problems with it nipping up on me, unsurpisingly !!!
    luke has been clocked on his rg-50 around taupo at over 120..!!!!.. not bad for a bike that has nothing done to it...


    what a ride so far!!!!

  5. #35
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    30th March 2004 - 11:00
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    I read some time back (but no doubt it's still true) that a Honda 50 engine from the 60s still holds the record for the power/litre for a naturally aspirated four-stroke engine.
    ... and that's what I think.

    Or summat.


    Or maybe not...

    Dunno really....


  6. #36
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    Quote Originally Posted by vifferman View Post
    I read some time back (but no doubt it's still true) that a Honda 50 engine from the 60s still holds the record for the power/litre for a naturally aspirated four-stroke engine.
    I read that recently, except I'm not totally sure it was the 50cc GP engine. 22,000RPM in 1963 -- damned impressive.

    Meanwhile, I hear Hondas are for fags

  7. #37
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    17th May 2005 - 12:20
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    Quote Originally Posted by vifferman View Post
    I read some time back (but no doubt it's still true) that a Honda 50 engine from the 60s still holds the record for the power/litre for a naturally aspirated four-stroke engine.
    Not 100% sure but I think that honour goes to the 5 cylinder 125 honda of 1963. From memory (not always reliable nowadays) it developed around 30bhp or 240bhp per litre. That really was something to listen to

  8. #38
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    Quote Originally Posted by eliot-ness View Post
    Not 100% sure but I think that honour goes to the 5 cylinder 125 honda of 1963. From memory (not always reliable nowadays) it developed around 30bhp or 240bhp per litre. That really was something to listen to
    Yep that sounds like the information I read... did you see my other thread on http://www.honda.co.jp/SoundofHonda/ ? Got a recording of that and many other Honda GP bikes.

    Also kensuem's link was pretty cool -- not such high quality recordings, it sounds like they've been taken off LPs, but they're from actual races. You can hear Hailwood go into the pits, and then a short while later run down the pits and bump start the bike. What a roar out of such a tiny engine!

    The 50ccs sound cool too, you can hear the Honda screaming away, sounding quite bizarre next to the two-stroke Yamahas; the same frequency as the two-strokes (revving twice as high!) but with a four-stroke exhaust sound. Odd.

  9. #39
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    Quote Originally Posted by xerxesdaphat View Post
    Yep that sounds like the information I read... did you see my other thread on http://www.honda.co.jp/SoundofHonda/ ? Got a recording of that and many other Honda GP bike
    Heard the 125 Honda and Suzuki live on the short circuits. Three times every race, Once in the pits, again off the start line, and then again half a dozen laps later when they lapped me, but for sheer noise level the MV 125 had them beat. Shattered both eardrums and had hearing problems ever since.

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