Modern Vespa

Good evening. I got my bike at end of May. It has 4500 miles on it, and this week developed a problem with fueling. Or so it seems.

I thought I got a bad tank of gas, there seemed to be a flat spot in the acceleration at 30 and 40 mph. Slight, but noticeable. Releasing the throttle, there is a hesitation as the bike got to 30 mph slowing down. Then at under 10 mph, the bike feels super quiet, as it I had shut it off or pulled in a clutch lever, like a regular moto. It does not stall.

Bike starts, runs fine otherwise. Over 40 up to 70 or so, runs great. I took it on the freeway to Vespamotorsports, thinking a good hard run will clear it out. It did not.
At VMS, the tech took it for a ride, and was able to feel it.

I think he adjusted the throttle position sensor, and checked the air intake for leaks. Which would have the bike run lean at certain speeds/throttle positions.

He told me to ride it to see if it clears out. If it was a tight valve, Robot said it would have trouble starting. He also didn't think it was a belt/transmission issue, but a fueling one.

Tech said that the Euro 5 bikes are more sensitive, and if I did get a bad tank of gas, it might take several tanks for the ECU to relearn the throttle position. If I understood that correctly.

Yesterday I took it for a hard run of 50 miles, seemed to be less apparent, almost perfect. But on today's commute, which is 5 miles, I could feel it again.

I am halfway through the second tank since this started. If it doesn't clear up, Robot said I would have to leave it a few days so they can figure it out.

Anybody have any ideas? I would think it if was the fuel pump, it would either stall or quit. I have no trouble restarting, hot or cold.

Thanks in advance.

Sure does not sound like a fuel pump problem. And you are a lucky guy for living so close to a Vespas dealership. They will figure it out.

Thank you. That's what I wanted to rule out, if anybody here had that experience.

Well, it's not ruled out. I am not a Vespa Mechanic. These things a computers on two wheels and the guys at Vespa Motor Sports are factory trained and do this everyday. If it does not seem right, take it back to get it sorted out. It is great dealership who stands behind the products they sell.

Update: I left the bike @ Scooterwest to let them mess around with it.

Funny, when I disassemble the bike, it can take me an hour as I check and double check my work. I also have no power tools or lift. The tech had the bike apart on the lift in about five minutes. The clutch is fine, the idler pulley is rattling and is being replaced. A new belt was put on, I told Robot to go ahead and do the 6k service since the bike is there and apart already. It's a bit early, but so what.

The PAD tool showed that the oil sensing switch was not working (?), it's getting replaced.
It's only been a few days and I miss riding it.

are you sure you heard that right? the pre-2023 didn't have the oil pressure sensor connected to the ecu only direct to the led on the dash so pads can't detect if it is ok or not.

Lot of faults for a new scooter!
I'm thinking that unless you're buying your gas sold in Coke bottles along a dirt road....it's not bad gas. Not in N. America.
Just MHO, after more than half a century fueling in the USA.....
They'll get it sorted for you

O.S.

This is a 23. the light was working, the oil pressure sensor was not.

I got the bike back today, and it's running great.

We did the 6k service (I figured it was there anyway, the bike was apart, and at the rate I
am racking up the miles it will be just a few weeks before the service needed to be done).

Winds up the issue was tight valves, as suspected by the techs after test riding and inspecting it. I've had bikes that at the first valve adjustment, the valves were loose. Never had one with tight valves.

Happy to have it back.