Modern Vespa

Hello,

On the monthly SF Scooter Club ride today, my '20 GTS300 (350mi on it, purchased lightly used in Sept of last year) had a mechanical that is puzzling me a bit.

After riding around for 90min or so, typical SF stop and go, hills, bit of zoomies, usual crappy urban roads, we pulled to the side of the street to regroup, and when I hit the gas, the immobilizer/water temp light came on and the engine cut out. I didn't see the check engine light or anything else light up.

It wouldn't start again until I switched the ignition off and on again, then it ran for a few more blocks and did the same thing (and again started after another "hard reboot"). Luckily we were just 2 downhill blocks from our house at that point, so I rode/coasted it home without further issue.

The engine seemed pretty hot (but no moreso than my wife's Primavera 150 which she'd been riding with me), and my glasses, which had been in the glovebox, were warm.

After it cooled down I checked the coolant level, and it is just barely below the "min" marking. There was, however, coolant on the outside of the receptacle, indicating to me that perhaps when I had recently removed the cap to remove the glovebox, I had not screwed it on tightly enough.

I would not, however, expect any of that to result in the engine cutting out, which almost seems more like an immobilizer issue than an overheating one.

Obviously job 1 is to top off the coolant and ensure the cap is tightly screwed down, but does anyone have any other thoughts as to what the issue may be?

Rgds,
Adam

The immobiliser doesn't cause the engine to stop. It only can cause the engine to not start.

(But i don't know what the cause of your issue is)

Does this model have an actual temp gauge on the dash? If so, what was it reading?
Did the cooling fan come on?
Is it the original coolant?
I'm thinking the engine was overheating and shutdown to protect it self due to possibly a stuck thermostat or old coolant

So a GTS 300 from 2020 with 350 miles on it. Right?
(where did you find that? Did hardly 100 miles in a year)

There cannot be anything fundamentally wrong with it.

Ah good to know - that rules the immobilizer out It does not have an actual gauge, just the light. I don't recall noticing the fan coming on (I'm not sure I ever have noticed that, so not sure how noticeable it is). It's almost certainly the original coolant. I bought it with 100 miles on it, so not even that! Prior owner got it to replace a stolen Primavera, then moved and it sat in her garage and I bought it on a consignment.

I certainly *hope* there's nothing fundamentally wrong with it! Coolant will arrive tomorrow, and I'll fill it up and ride it around and see if the problem recurs, and in any case, I think I'll make the break-in service appt early and have them change the oil & fluids, since all are old, if not much used (I've read all the threads about older coolant acidifying and the like).

Rgds,
Adam

As an owner of the same model, I suspect that you would know if the fan came on—it is alarmingly loud and quite noticeable. The first time it came on for me, I thought the bike was going to explode and take me out with it.

You don't want to overheat anything, but getting the fan to go is pretty easy, just riding a little then idling. Crossing to SF yesterday with this weather, I managed to get it to go heading into the toll plaza just being super slow. Happens all the time to me in SF, as I idle and walk my way to through traffic.

Indeed. You really notice it when the fan comes on.

So I would fill the coolant to the specified level, and then, as suggested by besupa, go for a ride and then stop and let it idling.

After a few minutes the fan should come on.
If that does not happen and you get the overheat warning light, then most probably the thermoswitch is faulty, or there is a problem in the connection between the thermoswitch and the fan.

I would not expect that is the case considering the young age and the low mileage of your scooter, but you never know.

First make sure that the cooling works as should and then you can bother about the other fluids.

Perhaps a good reminder about periodic maintenance even if there is no fundamental problem beyond low coolant. The scooter is 4 years old so that first service would not be early. Oil should be changed a minimum of once a year regardless of miles ridden. The usual recommendation for changing engine coolant and brake fluid is once every 2 years.

if it's not temp issue (don't know) then it could be fuel pump issue. there was a recall for bikes from around 2020. ask your dealer to lookup your vin in their system

It shouldn't be the fuel pump as that arose on the 2021 and 2022 models.

That said, he could be really unlucky as there is no reason why it couldn't be the fuel pump.

Sound like you may have overheated it. Drain the oil and see if there is coolant in it.

This, plus coolant reservoirs have been known to split. I've had two in my time with a total of 10 Piaggio bikes.

Worst case it's a head gasket - here's hoping it was just a poorly tightened reservoir cap.