Modern Vespa

Today, riding home from my brother-laws, a mile away from his house, my scooter just shut off. Wouldn't restart. I had to push it into a parking lot. Tried a few times and the starter would run but the scoot wouldn't start. I pulled the spark plug and it was dry. Looked normal. I put it back in- about 15 minutes had passed- and it started right up and I rode home 15 miles with no problems. While I was visiting, my nephews more likely than not spun the throttle a few times while the scoot was sitting there- I've caught them doing it in the past. Think this may have been the cause? I'm not going to say anything to them - I'm just curious. (From now on I won't leave it around 7 and 9 year olds unattended . The scooter has over 12K miles and has never done this before.

Bob

New vehicles with carbs - aren't they supposed to have an automatic fuel cut-off, so when they're not running fuel cannot drain into the carb? If that is the case not sure the little monsters relatives could have done anything. If you are able to flood it while parked that would be a problem.

Was there a great temperature change while you were there?

Perhaps your little 'helpers,' were rocking the kill switch back and forth, and left it in the middle and it clicked to the kill position after a bump or two (50/50 chance right?) and your automatic sit on the bike response is to flip it on after it died?

No big change in temp. I did check the kill switch and it was in the proper position. Maybe the fuel filter is plugging up. I did flick it with my finger while I was messing with the spark plug just in case. I wasn't in the best part of town and it was getting dark. I was trying a lot of stuff. I removed the gas cap since the plug was dry just to make sure the gas gauge was working- had a half a tank. Strange happening. Kinda felt- stranded .

bob

Whenever I hear of an engine cutting out suddenly, I always think ignition wire. The wire really isn't held in place very well, at either end - the spark plug boot and the coil output have these little sheet-metal-screw-looking affairs, that screw into the wire conductor from the butt-end of the wire. Seems the factory doesn't assemble them very solidly, and they're prone to coming apart.

Happened to me. My 2¢.

Do you mean the spark plug wire itself? The part on the spark plug seemed secure but it didn't "snap" off like I thought it would. It did "snap" when I put it back on. The other end goes to the coil right? I'll check that end better tomorrow when it's light out. I did stick my finger in that area and check for looseness which I didn't notice anything out of the ordinary.
Our roads are bumpy so maybe something did come loose. I do wonder about the fuel filter though. It's never been changed. Maybe some dirt just made it to the opening and once the fuel in the line burned away it just stopped. My messing around and moving it into the parking lot may have opened things up? Just looking for the cause. Of all the places for this to happen, this wasn't the best.. I'd like to find the cause.

Bob

Bob: yep, it was the wire itself. It wasn't "screwed into" the spark plug boot solidly enough, and it eventually just fell off. The bike was running fine right up to then. Another guy had the coil-end of the wire come loose for the same reason:
https://modernvespa.com/forum/topic35486

+1 on the electrical fault. You can try wiggling the spark plug cap to see if a little corrosion has interrupted the connection. Otherwise, if the cap and wire seem fine perhaps the cdi has begun to fail? Mine did, had ages of starting difficulties despite a whirring starter before I figured out I was no longer getting a spark. On that note, if the cap and wire seem secure and wiggling it does nothing, I'd pull the plug and look for a spark (carefully).

Regarding the auto-shutoff on the modern carbs there is such a thing... it's a vacuum operated fuel tap. They do get gummy over time and fail to seal, but if the tap is in good working order no gas should make if from your tank to the carb when the engine is off.

Thanks for the link. That may have been it. I will check the other end tomorrow. Do you think the plug should have been wet with gas or dry like it was? There was no smell of gas anywhere.

Bob

Bob, tis issue happened to me shortly after I bought my scoot and I was very worried. When I callde my dealer he told me it was likely the spark plug wire. I was able to plug it in on the side of road and it worked perfectly. I hope it is an easy fix for you too.

Today after work I started the scooter and it started right up. No problems, idled beautifully. I rode it one mile to put gas in it. It had a 1/4 of a tank. After filling it wouldn't start. Just like yesterday. I pushed it to the side and waited 15 minutes and it started right up and ran perfectly home. WTF? It sounds to me like something in the carb, maybe dirt clogging things up. I did remove the gas cap again while I waited. Not sure if that does anything. I need help diagnosing this- I have a big ride planned for Saturday. Help!

Bob

A former MV member, Conchscooter, had an issue like this with his GTS. After many many trips to the dealer to get it fixed he finally gave up and sold it and got a Triumph.

It turned out (if I remember this correctly) that the fuel injection throttle body was loose and caused an intermittent problem of the engine shutting off. Simple fix but a long time to find it.

My scoot is a BV200 and has a carb. I'm thinking it's fuel related. I'm going to try and remove the fuel filter now and see what I find. The spark plug has only been in for 2400 miles. It's a NGK.

Bob

Sounds like the spark plug wire wasn't connected completely which would allow some turnover of the starter but no firing. First thing I always check is the spark plug connection.