so graham, if I drilled a hole in the head 10mm away from spark plug (exhaust side) and 5-7mm? short of going all the way through and putting my sensor wire in there and jb welding it I can imagine it would be much more accurate than soldered to a copper washer under the spark plug?
I fitted cheap chinese egt gauges to my Yamaha rd 350 after being told they give a quicker idea of impending meltdown than head temo gauges as the exhaust gas temp drops just before meltdown as deto occurs
what no one told me was the temp drops every time you open the throttle and the needles fly all over the place
all they are good for on my bike is novelty factor