a question of ratios for the airheads among us

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  1. Bikemad
    Bikemad
    hey there BFTPers.....i am somewhat confused........not unusual i know but this time i can be specific.......as some of you may know i have recently acquired an ex mot R80 which i am mucking round with in the shed and would like to ditch the original instruments and fit an aftermarket type jobbe.............these are the two i have been looking at

    http://www.trademe.co.nz/motors/moto...-544663079.htm
    60 kph @ 1400 rpm 140km/ph
    http://www.trademe.co.nz/motors/moto...-544952743.htm
    60 mph @ 2000 rpm 140m/ph

    so break out the casio people and do the maths........ i am aware they both will not be accurate as such but would like to get whichever is the closest....or are they in fact the same ratio......or maybe one of you beamer gurus can put me onto an accurate one of the same style............come in volty kick and max
    cheers ya'll
  2. Hobbyhorse
    Hobbyhorse
    I do not know which of those would be best but I do have a comment about revs etc.

    The R80RT I have just bought, and which is an ex police bike shows 4400rpm at 100 kph. I was expecting 4000 at 100kph but this one must have a lower geared final drive ... perhaps for escort work. Not too sure how this would play out on the two speedos you have shown.

    Rhys
  3. Kickaha
    Kickaha
    come in volty kick and max
    Leave me out of this my bike wont even have a speedo
  4. psyguy
    psyguy
    at the risk of further confusing things... but, wouldn't the speedo gear ratio have to do with the front wheel speedo gear NOT the engine rpm speed (as that indeed depends on the transmission gears) ??
  5. psyguy
    psyguy
    there's a chart for speedo ratios in this link that *should* include your model
    http://bmwmotorcycletech.info/ringgears.htm
  6. Bikemad
    Bikemad
    cheers psy for the link.............the speedo is driven off the final drive not the front wheel on the bm
  7. Kickaha
    Kickaha
    wouldn't the speedo gear ratio have to do with the front wheel speedo gear NOT the engine rpm speed
    BMW speedo works off the gearbox not the front wheel like the more primitive makes
  8. psyguy
    psyguy
    as i said, i spoke...

    psyguy - Today, 20:59
    ... at the risk of further confusing things...
  9. Voltaire
    Voltaire
    Real bobbers don't have speedos....
  10. Dieseldick
    Dieseldick
    Voltaire - Yesterday, 22:44
    Real bobbers don't have speedos....
    Report
    Results 1 to 9 of 9
    Don't you mean "wear speedos" Volty.
  11. Voltaire
    Voltaire
    speedo's are out.....
  12. Dieseldick
    Dieseldick
    Ain't that the naked truth?................nah, but it adds new meaning to "using an athletic support".
  13. ICE180
    ICE180
    look like he must ride a scooter with that Ghey get up
    al least he has his saftey gear on
  14. Bikemad
    Bikemad
    yeah fuck sorry chaps.......what was i thinkin.............posting a motorcycle related question on KB...........i must have rocks in my head.............as you were
  15. Motu
    Motu
    I've got a new scream saver. How was your afer work piss up ? I'm pissed.....
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