Advice – keep it simple
Too many people try to wire up these all singing and dancing digital speedo/tachometers and come a cropper. I may be wrong here, but I cannot recollect a definitive thread on here that explains what wires go to where to allow for speedo, indicators, neutral light, high beam, speedo light, tacho etc – it all gets “complicated”
All you need is simple tacho that takes a signal from between the HT coil and the plug to give you a pulse, with the ability to “halve” that signal (it’s a four stroke), and if you need it back lit, splice a feed from your speedo light
Recommendations – none. For one thing, I’m in the UK, and for the second, my ears tell me when I’m over revving a TW. The power drops off, my fillings start to fall out, and by-standers start to stare …..