Modern Vespa

I've got a brand new 2023 GTS Super Sport. So far I've got about 300 miles on it. Maybe 50% of the time when I start it from cold, it tends to stall about two seconds after I start it, the first time. Then it's fine after I restart it. Maybe feels like its revving slightly slow, but this is my first GTS so I don't know what's normal.
Does this sound like reason for concern, or should I just wait for my 600 mile initial service to sort things out? I'm told it could be the ECU 'learning...'

If your dealer is close by, why not schedule a time for them to look over everything? If not, I'd make sure they comb over everything during the first service.

Check battery voltage

Are you twisting the throttle when starting? Just press the button without touching the grip.

Thanks all. I was able to get the GTS into the shop, and turns out it never got a software update it was supposed to have before it left the showroom. It's done, and I can feel a noticeable difference in how it runs (not rough like it was). Time will tell if this fixes the stalling on start issue, but I'm pretty confident it will.

All of my 2023 models do the same thing. But I only ride one (out of 8) every day. After I ride one for a couple days in a row, it will start on the first try, but even when tendered, it's like the fuel pump doesn't push enough fuel into the right place. Sometimes they start without any stalling even after a week. Not sure why the variance but there is a variance in how they operate.

Bug,

Have you seen any difference with the software update? All of mine still do this but I attribute the issue to switching them out every day.

I thought I did. But it's still happening. I left the GTS with the shop for the weekend so they can start it cold and see what's going on. I'm lucky to have a great shop here in Portland that'll sort it out.

I still think the software update made the engine run slightly smoother, when it's running... But that might just be in my head.

Mine all do this too, all 8 of them and they're all 23 GTS 300 models. I would worry if only one or two of them did it, but they all do… let me know if you happen upon a fix

Have you had any luck since your Vespa was in the shop or does the problem still occur?

It's been in and out of the shop 14 or so days since I got it a month ago. The final diagnosis was a bad ECU.
Apparently the ECU was throwing a code that signaled a communication issue between it and the electronic key system. The shop called Piaggio with the code and Piaggio said this is a known but rare issue that causes the bike to stall on first start. They authorized a replacement ECU, which the shop had to pull from another new GTS, since getting a new ECU might mean weeks of waiting...
Anyway. Long story short, since the issue only really happens after its been sitting overnight or whatever, I won't know if this really fixed things or not until morning (just picked it up a few hours ago). Crossing my fingers, and thankful to the techs who spent so much time diagnosing and fixing this...

Crossing fingers for you too! Please make sure to let us know how the "fix" works.

Sadly I don't think it did. In fact it's worse. It stalled on three out of five starts today, none of which were cold starts.
I'm really at the end of my rope. Half of the one month I've owned it it's sat in the shop, and it's still not resolved.

I really didn't think that would fix it.

Did you add a different gas cap by chance? I think it's related to the fuel pump either way. I noticed that on certain vespas, if I turn the switch to let the pump actuate twice, it doesn't have the issue but that could be coincidence.

Also, you might try going on a long ride. Make sure the tank is filled with 91 octane or better. Blow out the fuel in the tank and get your enjoyment out of it. If the problem then persists, seek a return. I can tell you, having 8 23 GTS models, some of them do this from just not riding them everyday. Once I ride one for a couple days though, I have no issues generally.

What if it is still the ECU, your 8 GTS still also have the same problem? Maybe the ECU shop scabbed off the new GTS was also bad?

Or the ole dreaded too much gas in the emissions canister?

Huh. I hadn't thought of that, actually... I wonder if they re-checked the codes after they installed... That was the first thing they tried.

Yes, for me it could be too much gas because I often get close to the top of the chamber, even using the Gas Funnel that Scooterwest sells.

Here's my fix, which seems to work all the time. I believe this issue is related to the fuel pump/pressure at early morning start. It's been warm here lately and I think the pressure of fuel into the system drops a bit hours later. What I do is turn the ignition 3 times, such that you hear the fuel pump pressurize three times. Then I start it and it starts every time, without the engine cutting out at all. If I do it twice, sometimes it will die. If I turn the ignition to pressurize the system just once (as we should be able to), the engine may or may not stay alive -- but three times, it works every time!

All 8 of my GTS's do this. Sometimes they don't and sometimes they do. Totally random and not unique to any one Vespa. They seem to run fine all day and not require more than one "Pressurization" by turning the ignition more than once as the day goes on. I think the fuel pump doesn't run long enough to pressurize the system and that's where the real issue is, because it can be overcome by doing the above!

I never noticed this in the cooler months but it may not matter. All of my GTS models have the updated Fuel Pump, not the faulty one that my 22's had.

Too much gas seems like it might be culprit, my 2018 GTS has no charcoal canister, even still, when gassing up at Chevrons mostly sometimes gas will pour out of the fuel vent drain hose onto the ground, if the charcoal canister was still connected it would have been swamped.
I wonder if you were to have 1 of your GTS de-smogged if it would only need one fuel pump start up to be on its way.

I thought so too! Im more careful about filling now as I know about how much to fill given my riding style. It doesn't seem to matter if the Vespa is half tank or full tank though, but I guess is the charcoal canister hasn't evaporated yet, the problem could still exist. I also went back to the standard Vespa gas cap and that could help too?!? The nicer metal ones are crap, unless you go with the Piaggio branded metal one.

Anyway... My GTS is in the shop again. Changing out the ECU definitely didn't solve the problem. We're now suspecting something is indeed wrong with the fuel pump/pressurization.

Here's what it does when I start it cold (although it's happened a few time starting a warm engine...)

For those keeping score, this will mark total days in the shop at something like 15. I bought it July 8.

https://www.youtube.com/watch?v=zwywicLHL1o

Try waiting until you hear the fuel pump stop whining, looks like you're starting it before it's ready to go. Sometimes when cold, I will let the pump run twice, the. I never have the issue.

Indeed I tried the prime-it-three-times thing as suggested a few posts back but that didn't work, unfortunately. But yeah, usually I'm not so quick to hit the starter. I'll have to go back and look at other videos I made of this issue to see if I'm doing the same thing...

Either way, you shouldn't be having so many issues with it. That's not normal. Because I ride one of the 8 vespas (different one every day) the same one doesn't get written twice generally, so I always double prime it, and rarely have any issue.

I also discovered that the ones with the gas cap that's not original tend to have more cold start issues. The aftermarket gas caps, so I went back to the originals.

It does have to turn over at least two times before the ECU works out the correct firing timing. Give it more than half a second to make its mind up!

Sorry to hear about this. The dealer needs to make this right, and you are luckily still under warranty. I had a problem with my 2015 GTS's ECU/throttle body assembly a few years ago (out of warranty) - it sucked. Good luck.

If you bought it at Vespa Portland, Andrew will take good care of you. He's a great guy that knows what he's doing. I can't wait until this is a good situation for you and you're enjoying your new Vespa, you're really going to love it once it is behaving properly.

Yup, they're great folks. I'm sure this is frustrating for them as well, as it's eating up a lot of shop time... I half-considered just living with it for now and dealing with it in the winter, when things are slower, but didn't want to risk waiting that long in case this turns into something major...

I think I can finally close out this thread. The problem seems to have been solved.
It was not: gas in the evap system, the ECU, or the fuel pump. Turns out it was that the valves were way too tight from the factory. They've been adjusted to spec and now it seems (after one day of testing at least) to run like a dream! So, if you're having this same issue (stalls a second or two after start the first time, then starts right up but sometimes runs a bit rough), have your valves checked.

fingers crossed

That sounds spot on! So many things are too tight right out of the factory! Fingers crossed and happy motoring