Modern Vespa

From time to time my Vepsa engine will cut out. This only happens when I am coasting (as in not twisting the throttle), frequently going down a hill, and normally within five minutes of starting the engine.

Sometimes, it happens once, other times it will happen many times in a row. I am always able to start it back up.

Thank you in advance if you have any ideas as to what might be causing this

First, clean the air filter and the throttle body idle bypass:
https://cheekythoma3.wixsite.com/itsme/idle

If no improvement, check the valve clearances.

For clarification:
The engine is running fine and you drive at a steady speed. Then suddenly the engine cuts out, as if you would have pushed the kill switch. If it happens it is only in the first 5 minutes after a start. It is no hesitation, it cuts out and does not re-engage until you are at standstill.
Then you restart. And so far that is not a problem.
Something like that?

That restarting: do you have to wait a while until restarting is successful, or does it restart instantly?

Does it also happen after a warm start, so when the engine is still warm after a short stop like filling the tank?

When it cuts out is there any warning light coming up?

Sorry to jump in on your thread my GTS 250 stalls out but I only just noticed it today. Fine on a freshly charged battery which is not the best in the world but after 3 or 4 starts it cuts out at idle. Don't know if that could be the cause of mine and also maybe yours.

Correct it never happens when I am twisting the handle to go faster/maintain speed. It only happens when coasting. Also correct Yes that is exactly what happens It typically restarts instantly when I try No only cool starts, typically the first time I am driving for the day. I haven't noticed any warning lights when it happens, but will check next time. The headlight and tail light do stay on after the engine cuts out.

Thanks for the help!

This sounds like a different problem. My Vepsa starts fine and I can drive, but then the engine cuts out if I coast shortly after starting. I cannot recall it happening after driving for 20 minutes, also sometimes it happens multiple times in a row.

At Climbguy:

I see. Coasting. You mean with closed throttle.

The ECU cuts of the injection then, which is normal, but should pick up when the engine comes close to idle to keep it alive. And that is not always happening within the first, say, 5 minutes after a cold start. So when the engine is still cold.

For some reason when the engine is still cold the ECU does not seem to always recognize the engine is close to idle. But it does not detect a fault in the system because then the engine warning light would go of.

Then you restart. Goes without any issue. You do not have to wait or anything.
That means the ECU finds all the conditions for starting are there. I expect you start the engine throttle closed as is prescribed.

that is correct JimC based on the additional details should I try to clean what you recommend?

Based just on your first post - yes!

Kicking an older post. Has anyone found a definitive answer to this question?

I just found an excellent deal on a 2020 with 7400 miles.

I've had it about 10 days and 500 miles and it has stalled on me almost every day at the 5 to 10 minute mark into my ride.

The non-vespa dealer where I bought it is going to try to fix it but if he can't he either drops it on me, or has offered to "unroll the purchase" which I thought was honorable of him since his mechanics have 0 Vespa experience.

I sent him a link to this email to hopefully give him a start.

I'd rather not lose the deal, I got it for $4500 which was almost a steal since it had around $1500 in accessories already on it as well.

If we do have to unroll the deal i not only lose that but the $600 in tax/title/license I also have in it.

Honestly if he can't fix it I'm in a quandary whether to keep it, and try to figure it out or not. I'm so/so with a wrench but do know how to use torque wrenches and gap valves when it comes to it.

If I give it back I'll probably just buy a new one but that's mucho bucks with the dealer bull added in (these guys were only $500 added OTD which I might get back anyway). It might also take most of the summer because I would probably have to order what I really want for that kind of money so I lose the riding season on scooters and have to fall back on my Himalayan (not "that" much of a sacrifice but you know what I mean ).

I'd really rather fix the current issue if possible. Has anyone definitely resolved this one.

My issues sound very much, almost exactly, like these. Today on the way to the dealer thought I was 10 minutes from the house, like usual but had just hit 50 so not sure if I was accelerating still or had let off already when it died. I usually come to a stop before restarting but this time, since I had the speed on, I just turned off the key and turned it back on while brushing the brake lever and it fired right back up doing around 35mph at the time. Not sure if that changes anything, it wouldn't seem to from my understanding of what the issue could be.

Sorry for the long post, just hoping someone has gotten it figured out.

TIA for any input.

Bruce

first two half arsed thoughts ...

fuel pump. around the 2020 there was a fuel pump recall. ask the dealer to check (sadly you can't check for this particular recall yourself on piaggios recall site). although your description doesn't really match the typical pattern for this.

evap system.

plenty about both these issues on this forum.

Not sure how fuel pump or evap fit into a "stalls after 5 minutes on a cold motor but then starts right up and runs for a hundred miles"?

Again, I'm the new guy and really looking for input. I've read a lot about the evap issue, and a few things about fuel pump issues but I'm not getting the connection for this set of symptoms.

Can you suggest how these symptoms might relate to those causes?

Much appreciated.

Bruce

as I wrote it I changed my mind about the fuel pump.

but the eval .. not sure as I don't have the evap in my scoot here in australia so haven't payed a lot of attention to it. I'll let someone else comment on the likelyhood of that.

but really more pondering is needed.

is the stalling at idle (or very low speed)? if so it could be battery

I see where you're going with the battery/stator question but at the time I was doing around 80kph so don't think so.

The earlier description about cleaning the throttle body bypass port seems more in line with the symptoms so I was hoping that someone had actually proven this out, or found a likelier/definitive solution.

I have a couple of days to make a decision and hope this can get resolved. I'm actually pretty good with sophisticated analog/digital technology but intermittent vehicle electrics can drive you insane and I really don't want to buy a problem of that nature with a new/used scoot.

Again, thanks for the input...

Okay, time for the summary.

When i took it to the dealer they said it was on the fuel pump recall list. Had it for a few weeks while they waited for the pump and then returned it to me.

While they had it they said they also saw significant fouling on the spark plug so they replaced that as well.

I've put another 1000 miles on it since then and it only stalled one time over some bumps. I turned the key off and on while it was still rolling and it jump started and kept on rolling. No more stalls in the next few hundred miles.

Trying not to draw any conclusions from insufficient data but I'm guessing 2 problems of which the major one was resolved with either the fuel pump or the spark plug (possibly loose wiring?).

The remaining stall could be the wiring working itself loose again, or even an issue around the ignition key, don't know, just hope it doesn't suddenly get worse.

So far, so good. Haven't ridden it in a couple weeks but its been a mild winter in the NorthEast so far so maybe i'll get it out again before I start working on the winter fix-ups for it.

Thanks for the update. There is always added value when people share what they did to solve a problem.

You are right: 2 things have been changed and the problem seems gone (maybe not completely?) and therefore it cannot be concluded what of these 2 was the rootcause.

In problem solving it is a known approach to think things over and come to a list of potential rootcauses: it might be A or B or C and so on.
Then replace them all and see whether the problem is gone.

If it is gone then you know the real rootcause is in your list of potentials.
Then go back to original one by one until the problem returns: and that is the rootcause.

If it is not gone you know you are on the wrong track and you can bring all what you have changed back to what it was, and look further or think deeper, and start all over.

On that remaining stall I think you can rule out wiring working itself loose again.
You managed to restart the engine while driving. Loose wiring will not refix by itself.

PeterCC said: In the days of carburetors I would have agreed. Nowadays with so many electronic control systems I'm not sure that is such a guarantee anymore.

On the other hand, I don't know the Vespa electronics well enough to know if a signal being temporarily opened or grounded by a hard bump could cause the electronics to go into a "I'm not running now" state.

Turning the key off and on again is basically a power cycle of the electronics into a "ready to run state" at which point the already rolling motorcycle is the same as hitting the starter switch to start turning the motor over.

I definitely did not have to hit the starter switch for it to restart the motor, it just jump started when I turned the key back on so I can't help but think "power cycling the electronics".

On the other hand like I said before, I don't know crap about the Vespa electronics so time will tell I guess.

The usual suspect for intermittent stalling is the spark plug cap. The little wire C ring inside that grips the top of the plug weakens over time (corrosion?) and allows the cap to become loose.

Or it never gets seated properly because the location makes it a pain in the ass to push it on.

That too - so if anyone else has been at it (like the dealer) since you yourself checked it, that could be a clue.

I can see how a loose spark plug cap would cause it to miss, or stall and never restart if it totally lost connection.

But how would in cause it to shut down, and stay shut down, and then run again once the key was cycled 2 seconds later while it was still rolling?

Just not understanding that.