05-07-19, 04:24 AM
(04-07-19, 05:34 PM)Grahamm link Wrote: [quote author=Millietant link=topic=25425.msg300191#msg300191 date=1562251927]
For many years I've heard that most (80%) of the wear and damage in an engine occurs during start-up and shut down.
I could see that for starting from cold, but I'd have thought that, for a warm start, it wouldn't be an issue.
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When starting from "hot", the oil sitting on the bearing surfaces has still carbonised and the engine has lost oil pressure. Starting from cold is worse, but using the same logic, starting even from hot still causes more damage than leaving the engine running - although, as others have said, if it was a hot day and I was waiting at a level crossing for a number of minutes, on an air-cooled bike, I'd switch off at the key (to avoid possible overheating).
I wouldn't worry with a watercooled engine, as the thermostat would kick-in the fan to keep the engine/coolant temperature at an appropriate level.