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Re: Normal operating temperature

John Childs
Hello Charlie,
Your mail gave me the excuse to do an experimental lunch break potter in the sun. On my 1944 M20 I did 20 miles of open road riding at an ambient temperature of about 25 C. Immediately on stopping I recorded the following temperatures. Base of plug, 210; base of barrel, 98, carb body, 35. After 5 minutes at rest the same points measured at 175, 86 and 53. After 10 minutes; 150, 84, 56. After 40 minutes, 74, 54, 43.
So our head temperatures are pretty similar. Even though the carb absorbs heat out of the engine when there is no airflow or fuel vapourisation, my new Tufnol carb spacer is obviously doing an effective job of slowing the heat transfer down sufficiently to keep the temperature below the boiling point of petrol (approx 95C).
Hope this is helpful.
Thanks John,
I an a little at ease now. I figure my tapping sound was the decompression dow hitting the exhaust valve collar. All quite at engine start, but got louder as the engine temp increased. I readjusted things. Going for another ride this afternoon.

email (option): cbhaws@verizon.net

Re: Normal operating temperature

My M20 is also new back on the road after a long lay-up, and suffering from reluctant starting from hot, so I don't offer it as a perfect role model. It would be interesting if anyone with a confident good runner could offer similar data. I got my IR thermometer as part of a tank sealant kit. There are identical ones on Ebay for £10.95 (black and yellow body).

email (option): John.childs1@btopenworld.com

Re: Normal operating temperature

On my M21 on a hot day(around 100F), I have measured the cylinder head temp at over 500F. The carb will boil over if you stop but the bike runs fine at these temps.

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