Modern Vespa

I've searched the forum but haven't found anything that addresses my problem specifically. I have a Vespa ET2 (2003 or 2004) that hasn't been ridden much over the years. Sometimes it will fire right up and when it does she runs like a dream. Other days she won't start for love or money, either with the ignition or the kick start. Sometimes she'll stubbornly refuse to start one day and then fire up on the first try the next day. I'd like to chalk it up to the inherent unreliability of beautiful Italian things (being something of an intermittently unreliable beautiful Italian thing myself), but I'm tired of getting stuck downtown. I've tested the CDI and it checked out when I tested it, but I'm thinking maybe it needs to be replaced anyway since the problem is intermittent and appears to be a spark problem when it occurs. Spark plug is new and I've pulled it out a couple of times to make sure it was clean. I tested the plug to the head once when it wasn't starting and didn't get anything. Seems to obviously be getting fuel since it runs great ... when it runs. Quite confounding. Any thoughts would be greatly appreciated.

Check your battery terminals to make sure they're nice and tight and corrosion-free. Also check the ignition wiring. When you turn the key to on and it doesn't start, does the red oil light still illuminate or is there no power whatsoever?

Yep. Oil light comes on.

I think you're onto something with a cdi replacement... or it's a hall sensor

Hall sensor?

It's possible it's the kill switch relay going bad. It's located behind the horn cover to your left as you look in. It kills the feed to the coil so it won't get a spark. Engine cranks but no spark. Just a guess and I can't find how to test it. Here is a link to one https://scooterpartsco.com/vespa/et2/et2-electrical/30-amp-relay-58002r-581139-58246r

Thanks. Fairly cheap and probably easy to install. Worth replacing along with other stuff I suppose.

its the sensor that picks up the spark signal from the stator....you can tell if its working properly by hooking your meter up to the two wires that come off it and goto the cdi...kick or try to start it and see what voltage you get...

swap that cdi 1st and let me know...i can help you with this ^^

OK. Thanks. Just ordered CDI and kill switch relay from Scooter Parts Co. Couldn't find hall sensor on there. Is there another name for it? Is it attached to the CDI?

Also, what voltage should I be getting when I try to start? Many thanks for help.

The Hall sensor is attached to the stator and you need to get the whole thing. When you crank the engine the voltage will be in the 10volt range.

i think somewhere between 0.5 and 1.0 volts should be fine...

if its super low, let me know...you might have to move the hall sensor a tick closer to the "rotor"...when i say rotor i mean that bell thats on the right side of the crank over the stator....there are magnets on it..dont worry, we can go over this together if your cdi doesnt work

scooterpartsco has hallsensors in stock usually...

OK. Thanks. Couldn't find Hall Sensor on Scooter Parts Co. CDI supposed to come Wednesday. Will try it Sat at latest and let you know.

https://scooterpartsco.com/vespa/et2/et2-electrical/stator-for-vespa-et2-and-piaggio-2-stroke-50cc

looks like it comes with the stator.. its that little square black box in the center of the stator in the picture... you can get it seperately....we can ask Motovista what the part number is if needed....

the gap just needs to be around 0.8mm or less than 1mm ...that spark has to jump more than .7

i just looked this up for another member...but this is a great read

https://www.pedparts.co.uk/blog/piaggio-ignition-fault-finding

Trace the stator wires from the motor to under the left floorboards. See if you can unplug the stator bundle from the harness (via a white circular plastic plug). Then try kickstarting the scooter. If it magically starts first time you have a short in the harness bundle. If you need to kill the motor, plug the white connector back together and as long as the kill switch/ key switch is at OFF, it'll kill the motor. If not, unplug the spark plug cap.

OK. So I just went out to try this and the damned thing started up in the first kick without me doing anything. So, now if I try this I won't know what the result is. Feels like I need to do it when the thing is not otherwise starting. Unless there is another way to test regardless of whether the thing is currently starting?

My test was just to eliminate gremlins in the harness. Sadly it only works when you're having issues.

If it's starting right now and you have the time to mess with it, turn the handlebars/ go for a short ride and see if you can get it to act up. Obviously close enough to push it home.

On a two stroke, before you throw electrical components at it, check the compression.
After that, if it's an ET2, it's almost always cdi or carburetor. Then it's vacuum leaks. Then start searching for electrical gremlins.

Could it be compression if it runs fine once it starts?

It could be just high enough that the bike runs once it starts. From the moment you first start a two stroke, the compression starts going down. Usually they are good for about 8-12K miles before you need to rebuild the top end though. It could also be that the carb isn't acting right on a consistent basis. If you are trying to run it this time of year, a slightly hotter plug might help a bit. I'm assuming you've checked and there is still an air cleaner in the housing.

Haven't checked for air cleaner, but I bought it new, so unless it came without one, it's still in there. Just went out to try it and it started right up with the electric start button and it's about 43 degrees here. Seems to present as an electrical/ignition problem as it's completely intermittent and when it works, it works fine. Am I missing something? Do you think it could still be compression? Bike has fewer than 1k miles on it.

Over time, the air cleaners in these bikes often break down and get sucked into the engine. If you bought the bike new more than fifteen years ago, it's definitely worth checking, even though it's a PITA.
Most of the times with an ET2, the problem turns out to be CDI or carburetor.

OK. Thanks. Well, I bought new CDI so may as well throw it on there. Also, had bike pretty thoroughly checked out a couple of years ago when I lived in NY and was having trouble with it. Pretty sure they went through carb, etc. then.

UPDATE: Just went out and she started with the starter button. Shut it down and tried again and it wouldn't start, even after a few tries. Bolted in the new CDI and she started right up and even seemed to run a bit better. So, I'm calling that solved until I have trouble again. Which could be tomorrow I suppose. Thanks everyone for input.

Another thing to keep in mind with two strokes is that the spark plug has to reach about 450 degrees before it starts cleaning itself. If you start it up and then turn it off, you risk fouling the plug.

good job...toss in a new plug and off you go

Hope you will not face the issue in the next few months. I changed the CDI of my Vespa 3 years ago and so far no problem is faced.

Plug is fairly new. Took it out and simple Ted and she was in good shape.

. Autocorrect