I will be using a digital hour meter/ tachometer on my next build.

Works on all 2 & 4 strokes
Internal battey
Displays RPM when engine is running automatically displays run time in hours when motor is off
Programmable service check function helps precisely schedule needed maintenance

My local Go-Kart shop has one, here is the same one for a few $$$ more from Northertool.com part # 160590

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