Modern Vespa

I was stuck in three lane stop and go when it was 100 out at the top of a hill. I went from cruising at 65 to stopped, then constantly having to accelerate uphill. Temp light came on right away, so I pulled over, pulled out the bucket, and checked the coolant level. Coolant level was fine so I got back on it, turned the key, and the light was already off. I'm thinking the Fan wasn't on until the start of the stop-and-go and the temp light came on before the fan could make a difference? Rest of the ride was fine, and I watched it like a hawk (gave it a good 30 minutes to rest as soon as I got to another exit).

I guess my question is: is there anything I should look for in terms of problems caused by heat? I've had cars blow on me in the past and it makes me paranoid. Does the light come on well ahead of the "too late" point?

confused. I don't remember the GTS having a temperature light ...? where is the light on your dashboard? what is the symbol on it and what color? the coolant reservoir is not under seat (I assume by the 'bucket' you mean the under seat storage)

Yeah, there's a water temp light that doubles as the anti-theft blinky blinky. Taking out the under seat storage and checking the coolant were unrelated thoughts, lol. I pulled the bucket to let more air through, then also checked the coolant behind the right knee pad.

ah that makes sense

Not an attempted answer, just personal related observations:

On my Supertech I have noticed that when the engine is running at normal temperature of approx 85C and I then park and turn the ignition off and turn it on again a few minutes later that the temp has risen considerably typically to approx 95C.

This has made me wonder if turning it off is the right thing to do when temps are high enough for the fans (approx 105C). eg when stuck in traffic on a hot day. Sorta feel like the fans should be able to run when ignition is off ...


And another:

my engine bay typically runs at around 50C. Using an infrared camera I see that areas like the airbox etc are running at this, I'm not talking about the cylinder or head. There's also a temperature measurement that I am able to record* via bluetooth on my supertech that I believe is called 'air temp' and it seems to match this temp. I suspect this is the temp of the air in the throttle body. Makes me wonder if I should somehow modify the snorkle air intake that we have here in Asia/Pacific (different to North America and Europe) or find a way to direct more fresh air into the bay


* just one of the ways that my own app is better than the standard

I'm pretty sure they can. On my GT200, if the fan is running when I park, it will keep running after the bike is turned off (presumably until it reaches the lower setpoint temperature). Of course the new GTSes will be even more sophisticated.

On some Yamaha scooters the fan turns off when you turn the ignition key OFF while on others it continues to spin (at reduced speed) until the required temperature is reached.
On mine the fan runs together with the motor shaft (it is not electric).
On some Vespas I have heard them turn even with the key removed and it would be correct given the arrangement of the two radiators.

It's normal for the engine and engine bay temperatures to rise after tuning off the motor. It's called "heat surge" and arises from the sudden loss of circulating coolant and air through the rads. In addition, all the engine components become "heat soaked" due to lack of oil circulating which also removes heat from inside the engine but is no longer doing so. It's normally nothing to concern yourself about if fluids are ok and in these circumstances. I'm guessing that the op's bike was very hot indeed after higher speed travel and then coming into traffic with an uphill travel at very slow stop start speeds. The bike can cope with that ok as long as the fluids and oil is fine.The momentary flash of the temp light isn't necessarily anything to worry about as long as the fluids are ok.

Check the fan is operating by letting the bike idle after a run. It might be worth bleeding the coolant to be sure there's no air trapped in the system, those are the only things I'd do. Just because the 'temp' warning light comes on for a short time doesn't mean something is damaged, or going to be damaged. The most common issue with an over heated motor is alloy cylinder head warping! But that takes quite a bit more heat and a lack of coolant to make that happen! Your motor is safe. Don't worry.

Hmm, didn't think that they did but I could easily be misremembering. don't remember this being the case on my old 2009 GTS300 and haven't tried on my 2019 Supertech but it's sooo rare that I have experienced the fans coming on that I could easily be wrong.

Mind you since the water pump on a gts is mechanically part of the motor (ie not electric) I am not sure that it would be worth keeping the radiator fans going as the coolant wouldn't be pumping from the engine to the radiator ...?
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Fans work with ignition off on the GT125 and GT200, not on any GTS.

The GT fan is controlled by a temperature switch in the coolant feed, right beside the LH radiator.

The GTS fans are controlled by the ECU, responding to the temp sensor on the block.