Can I put a temperature gauge on a air cooled engine?

Yes there is no reason why not! A Temp gauge is as important for a air cooled engine as it is a water cooled one. So how do we do it.
1.Air temp gauge. If you look at the digital gauges you will find a digital temp gauge with a probe sensor. You drill a 5mm hole in the tin ware surrounding your engine, insert the tip of the probe and bond it in with epoxy.
​2. Think outside the box.  Fit an oil temperature sensor and gauge. The only difference between a oil temp and a water temp gauge is ........NONE! So use the sump plug to mount your sensor do the wiring and, jobs done!