Charon wrote on 02/03/09 at 08:54:00:J C Whitney used to sell a cylinder head temp gauge for Volkswagens. The sender was an item like a spark plug gasket, which was used to replace the gasket on one of the plugs. Seems to me it might mount in place of, or in addition to, the gasket on the oil drain plug and provide a temperature reading. I believe a similar item is still available from aircraft sources. If you got two, you could also have cylinder head temperature. If I remember correctly it was a thermocouple type device and did not require external power, unless it had a lighted dial. True, it would not be immersed in the oil, but the aluminum engine case is a pretty good heat conductor.
Yes, I remember something like that for competition Fiat 500s...
I believe it was called a "pyrometer", and read the combustion chamber temperature...
...in fact, it could read as high as 400'C !!!
I'll see what the guys at Suzuki say tomorrow... I'll show them my bits ...