It would be easy to monitor motor temperatures with a spark plug thermocouple (ebay $15) and a $4 HF digital voltmeter. Or maybe rob some thermocouple wire from a gas heater.
An air leak , from a failing main seal on some 2 strokes, could cause a too lean condition, overheating and trashing your motor.
This shows how:
How Thermocouple work? How hot is a lighter flame? - Thermocouple experiment
This sensor is to be installed between the cylinder head and spark plug hex to monitor cylinder head temperature (CHT).
The Cylinder Head Temperature Sensor (CHT Sensor) is designed for surviving high vibration and temperatures up to 752 degrees F (400 degrees C). The sensor will fit most 10 mm spark plugs.
The sensor cable is over-braided in stainless steel for heavy-duty abrasion resistance. The signal wires are Teflon insulated. Designed to deliver high performance, high temperature measurements, reliably and consistently in the most extreme operating conditions.
The high temperature sensors of choice for professional racing teams, R&D test labs, and Enthusiasts. The CHT sensors can be used for many different applications, including… but not limited to… Karts, Drag Racing, Formula 1, NASCAR, Off Road, Snowmobiles, and Boat Racing.