Hi y'all. I hoping someone has done this in the past although I canne find any topics when I searched.
I have purchased a DATATOOL Digi gear indicator (fleabay, where else!) :) this needs a signal from an electronic speedo. My GPS speedo doesn't obviously give this.... (an Indic8tor before you ask!) so my idea is to use a speedo sensor from a VFR750 or VFR800 or early Fireblade etc. which fits where the NC23 (and NC29) mechanical drive fits onto the final drive sprocket. By cutting / grinding off the mechanical housing and gubbins and making a mounting flange for the electronic drive to bolt onto. For this application it just needs speed related pulses, doesn't matter that the gearing maybe different(giving wrong actual speed). I know you can buy speed pulse generators for about 40 squid, but half the joy of this project is to find an elegant solution that is cheap. With the necessary speedo sensors available on ebay from about £18 I'm just waiting for a cheap one to turn up!
If I make a success of this I'll post details, but as this is for a track bike it may only be of limited use ...

I've now got a NSR250 electronic speedo sensor from eBay for £3.99. And I've discovered that the NC29 already has a separate, ie unboltable, (mechanical) speedo drive and the NC23 final drive cover is a completely different shape...
I may just make a flat plate and mount the drive on this and space it out on the original bolts for simplicity. More details soon.