Author Topic: Just connected AM koso speedo to k75, tach not reading correct or is it?  (Read 5850 times)

Offline Oliver

  • ^ Motobrick Curious
  • Posts: 102
Hello as I said I just put on my aftermarket koso speedo on my 94 k75 and all is well thanks to a conditioning circuit made by a friend for the speedo and sans the fuel gauge as the k bikes resistance is strange when it comes to the fuel gauge. (something I also need help with by the way)

HOwever the tachometer seems to be reading different to what the motometer was. normally 73 mph equals fifth gear at 5000 rpm on the original motometer however on the new koso unit it reads that when I feel the bike at top comfortable speed (normally around 73mph at 5000rpm) the new speedo says i am only at around 4300rpm so it is not a gigantic difference but definitely noticeable. So maybe the original motometer is wrong (which is most likely true, however Ive heard of the OEM speedometer being incorrect but never heard word of the tach being off) or the new KOSO meter is reading incorrectly. Any ideas?

ALso does anyone know a way I can use the original fuel level sender on the new koso? The koso has two different settings for the fuel gauge at either 100 ohms or 510 ohms but IM guessing these all run opposite to bmws fuel sensor.

Offline wmax351

  • ^ Quintessential Motobricker
  • Posts: 1237
Re: Just connected AM koso speedo to k75, tach not reading correct or is it?
« Reply #1 on: January 06, 2014, 04:13:22 PM »
The speedometer on the Kbikes is almost exactly 10% fast. 6000 RPM in 5th on a k75 is equal to 80 mph actual.
  • Albuquerque, NM
  • 91 BMW K75 Standard, 98 Moto Guzzi California EV
Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline Oliver

  • ^ Motobrick Curious
  • Posts: 102
Re: Just connected AM koso speedo to k75, tach not reading correct or is it?
« Reply #2 on: January 07, 2014, 02:56:42 PM »
Right but Im talking about the tachometer. My new tachometer is set up to have one pulse per revolution just as the original MOTOMETER is but where the motometer would say 5000rpm at around 73 mph the new koso unit i put on says it is at around 4500 (+/- 100) when I can feel I am at 73mph or so. So Im wondering if maybe the original tachometer was also 10% faster than what the rpm's actually are.

Offline Brad-Man

  • ^ Proficient Motobricker
  • Posts: 360
Re: Just connected AM koso speedo to k75, tach not reading correct or is it?
« Reply #3 on: January 07, 2014, 04:21:18 PM »
http://www.endtuning.com/gearratios.html

Above kink is a calculator that you enter your parameters into.

For a stock K100 RS w/2.82:1 final drive I got 4250 RPM @ 75 MPH.  (31/11) final drive.  Stock rear tire...

For a K75 I'm not sure of final drive ratio and tire size and possibly 5th gear ratio, but have at it and let us know!
  • Marietta, GA
  • '85 K100
Toys don't make the Man - Man makes the Toys...
'74 RD350
'75 RD350 w/Modified 400 engine, Chambers & MZB iggy

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