Modern Vespa

Happy to be of service, Scott. Ride on!

This morning it was hard to start again. After it warmed up it ran fine, good actually. It started right up after work. I have a long steep hill to climb on my way home and when I first got my scooter it flew right up it, 60 mph easy, but after the tank overflow it's never been the same. I could only get it up to 58mph at full throttle on the same hill. Today, after removing the evap system the power seamed to be back but after warming up it ran pretty rough and even died once at a stop light on my way home. It was really hot out, 98 deg. It did start right back up and I was on my way.
Oh yea, I didn't think to mention before. I was standing next to it one day with it running and when I went to get on, remember I only have one hand, I twisted the throttle just a little by accident and dropped it on the right side. I just stood there in disbelief. It was still running when I picked it up. I didn't notice any difference in the way it ran after that incident, I just thought I should mention it just in case it could have caused a problem. Thinking about it now, I guess gas would of had to get in the evap system from that. This was a few weeks before the problem started.
The problems didn't start until one Saturday when I went on a poker run. On the way there I was going down the freeway, when looked down at the speedometer I was doing 78mph, I was really surprised. I was probably going that fast for about 10 minutes, max. I stopped and got gas just before the run started, that's when the pump didn't shut off and gas went everywhere. I soaked up as much of the gas as I could from the tank neck as I could with a rag before starting it. Right after that is when all of my problems started. It was hard to start and it wouldn't stay running with out the throttle open a little. After a minute of holding the throttle slightly open it would stay running.
Well that's the whole story. Any thoughts on what might be the problem?

If you haven't done this already I would take the air filter out and check it. Laying it down almost certainly got some fuel in there but even if it didn't I would completely clean and reoil the foam filter pad as well as clean the air cleaner box as best as I could with a rag. It is sort of back to basics in my book, the fuel injection delivers the fuel so you can pretty much forget about that. The air filter box delivers the air for the mixture, cleaning that may help. After that comes electrical. I don't know how many miles you have on your spark plug but replacing that couldn't hurt and also checking the spark plug wire connection. My money is on the air filter. Keep us posted.

A few others have suggested checking and cleaning the air filter too. I guess that will be tomorrows project, and the plug too.
I only have 1,056 miles on it.
I was reading the maint. schedule and it said something about a throttle lever adjustment. What is that? That sounds like something I should look at too. It really seems like it's idling to slow. It just takes the slightest turn on the throttle and it starts, stays running and idles smooth. Just a thought.
I really wish there was a complete service manual I could get that would go over everything in detail. I'm not a mechanic but I can figure most things out and do whatever needs to be done with a little guidance. I really hate to pay someone to do something if I can do it myself.

With just 1056 miles on your scooter I'm sure the spark plug is fine. I would check to see that the spark plug wire is on tight though. Unfortunately the Vespa workshop manual leaves a lot to be desired. If the air filter is not the culprit there is always the Vespa dealer. I know they can be expensive and most of us like to tinker with our scooters ourselves but sometimes that can be the fastest and easiest way to resolve a problem. If you have a good dealer or a good mechanic that is what they do all the time and usually they are a lot better than we are. With your scooter they have the electronic equipment to run full diagnostics while we have to just guess at it. Good luck, and I hope it is just the air filter.

There isn't a carb on a fuel injection engine.

Scott, this sounds like a saturated air filter from the tip-over that you had. Gas & OIL can run into the air filter if the scooter gets laid over on it's side. If you open it, you'll find out quickly if this is your problem. I would leave the throttle lever alone. That doesn't sound like it's the problem. I'd also check just to make sure that the spark plug wire is screwed tightly to the cap but I'm thinking that by the symptoms you're describing and the fact that you had a tip-over................ that it's the air filter.

I think you're right. I'm a little embarrassed, this should have been the first thing I checked. I'll have to do it after work today, in the 100+ deg.
In the manual it says after cleaning the filter to soak it in a 50/50 mixture of gas and oil then ring it out before reinstalling. Is there a specific oil I should use?

Scooter (and possibly MC) shops sell "air cleaner filter oil". It's a light-ish oil designed exactly for this.

But I generally just wring it out good, let it drip for a few hours, and then re-install.

OK, Thank you.
I just went out to see if it was going to start this morning and it started right up, on the first crank.
I'll clean the filter tonight and enter, what I hope is, the last post on this issue.