It's HOT! (For Scotland, haha)

[ScottishBadger]

Hi folks. First proper ride out on my recently purchased CBX today, as the sun is "splitting the rocks". Unfortunately, a bad accident (biker killed at the scene, sadly) on the only main road has closed that road and diverted all traffic onto the country roads.....
I got stuck in a long tailback of stop/start traffic, no way to nip past them as there was a constant stream coming the other way and the road is quite narrow. Then I noticed the engine was starting to get a little "tappety" and idle poorly.....
I took the next junction, turned around and went home, figuring the engine wasn't getting sufficient cooling in the heavy traffic.
Here's the strangest thing though - I know engine oil expands and thins out as it gets hot, but how much expansion is regarded as normal? I did an oil change the other week and ran the engine afterwards to make sure the new oil was fully circulated, and re-checked the level after letting it sit for 10 minutes - it was dead-on the top mark on the dipstick. When I went to check the oil today after I got home, it poured out as I undid the dipstick! Yes, it was on the centre-stand on level ground, same as when it had the oil change done! There's no fuel in the oil, so that has to be one heck of an expansion rate, is that normal? It's Motul 5100 10W40, in case anyone asks what's in it.

[Dynamohum]

I always ran Amsoil 10/40, four quarts in and four quarts out. Never had that expansion issue you mentioned. My 79 overheated a couple times in heavy traffic but my only symptom was a sticking clutch. Ran perfectly fine after cooling off. It’s not just riding slowly that overheats the motor it’s that in heavy traffic riding slowly all the ‘air’ the motor is getting is the heated exhausts coming from all the other cars in front.

[NobleHops]

If there was a lot of condensation that had not yet cooked off, it's possible that it's expansion in your oil accounts for the excess volume. That's usually visible though, the oil looks foamy.