R65 - 1981 New speedometer?

[NorR65]

I think the original speedo/tacho om my R65 looks too big and clumsy.
I have found a new speedo which think looks good.
http://www.nova-mmb.com/mmb_en.php
This is a mechanical speedo, I do not want an electronic one.
Have somebody tried to change their speedo for an aftermarket mechanical one?

[nhmaf]

Well, it is made in Germany so there is a chance that they'll have an appropriate ratio to match the driveshaft/final drive on your R65.   Personally I wouldn't want a smaller speedometer - as my eyes age (along with the rest of me) I am beginning to appreciate larger numbers..

[NorR65]

If I decide to buy a MMB mechanical speedo I need to know the K-factor. Does somebody know the K-factor for my R65 1981?
Final drive ratio 3.44 to 1, speedometer drive ratio (km) 0.793.
If not I have to find how to calculate myself.

Did You who have installed a Vapor or similar have to know the K.factor?
Thanks

[montmil]

The Vapor digital instrument utilizes a Hall sensor which is triggered by a rare earth magnet attached to the front brake disc. Being a modern digital piece of work, the instrument can be programed -using a provided formula- to calculate front tire outside diameter and this data is then manually entered into the Vapor. Works on any size wheel/tire combo. Bicycle speedos do the same thing.

Monte