Modern Vespa

Minor problem, but a bit of a PITA, so, if it has a solution..


Only notice this when leaving work. Engine cold, I'll start up and cruise through the parking lot, then stop and wait for traffic. That's when it happens. Not every time, but often enough. It will stall out, take a few seconds before starter will kick in, starts and off I go. It's like it's idling too slow. Never a problem otherwise, idles fine any other time.

Ideas?

Battery?

When did you last check the valve clearances? This is a classic sign of them needing to be adjusted.

Throttle body by-pass need cleaning?

When I reassembled the top end last October.

I was obsessive about getting them right.

Possible, but it's pretty new

That crossed my mind. Easy enough to check off the list.

Trouble is, as an occasional event it's not annoying enough to go after unless life gets boring. If it left me sitting in traffic it would be a bigger priority.

They may well have "settled in" since then - worth quickly re-checking.

Hate to admit it, you could be right. I'll have her up on the lift in a couple of weeks for routine fluids, etc, so not a bad time to look.

I had that issue with tight valves. It started happening more frequently over a few weeks, went away when adjusted properly.

When I last had my Vespa serviced at the main dealer, they showed how they have to reset the system following a service. He even demonstrated how mine would cut out with a fresh plug and fresh air filter as it adjusts over time to know these elements are worn.

I'm not sure if unplugging the battery for 5-10 minutes would reset force the Vespa to start with new parameters - but this would be my first thing to check as it's easy and free to do.

Engines need to run richer when cold, so my next check after this would be to run a fuel cleaner through, or try a premium fuel with one built in - and then a bit of "spirited" riding.

Do you also know when the fuel filter was last changed?

I'd also check valves as well, but I'd start with the cheaper / easier jobs and work up.

It hasn't. I follow the standard schedule, and either missed it or it isn't on it.

Not a bad idea, but wouldn't a clogged filter show up sooner at WOT?

The fuel injection system could believe there's a bit more fuel getting through than there actually is if there's a very minor issue with the fuel filter.

At full throttle, being lean by a few % would probably give you a tiny bit more power - but on a cold engine when it's trying to balance tiny amounts of fuel, being lean by a small amount could be enough to stall the engine.

Definitely try a battery disconnect as the first step though in the hope that the engine relearns its parameters.