Modern Vespa

Hi forum members! I haven't had much time to look into my problem yet but I'll give a quick rundown. Had this vespa running about 10 years ago for someone I know, they let it sit in their garage without touching it and wanted to get rid of it so offered it back to me. It doesn't start at this point and we can assume I have 0 knowledge on vespas. Just looking for suggestions so I can give some stuff try.

fire: does it have spark?
water: does it have fuel going to and thru the carburator
air: does it have compression?

does it kick over? shift it into neutral and activate the kickstart. does the bike lurch forward, if so, it may still be in gear, or the piston is stuck

id imagine a 10 year old battery needs replacing

take out the spark plug, then kick it over holding the spark plug (with protection) to the frame, is there spark at the tip of the plug? if so, plug it back in and try again

put fresh gas in, turn the gas knob to on, and try it a few dozen times to start the bike

you may have to remove and clean the carb:
https://www.scootermercato.com/Scooter-Parts/Carb-Gasket-Kits/154754-KIT

When I was doing my little bit of testing, looks like there's no spark. Didn't go looking for the battery but was smthn I was thinking about, would have to look to see where that's at and stuff later. It still has fuel but it's old stuff so kinda cycling fuel through hoping it cleans out. Kick starting it turns the flywheel and makes the lights flicker.

The battery is not relevant to troubleshooting spark, so don't worry about it until you have it running.

You'll need to drain the gas tank if you haven't already.

How did you test the (lack of) spark?

The best way is to remove the old spark plug, then get a new spark plug, put it in the cap, and hold it against the engine case while kicking it over. You'll be able to see it sparking.

If your lights are flickering, then the headset key is on. Did you also make sure the ignition switch on the handlebar switch is in the "on" position?

Post up some pictures of the motor and the headset so we can get a better idea what you're dealing with. That will help a lot.

And welcome!

I tested for spark using a spark tester then held the plug up against the chasis just in case the bulb for the tester had gone out. I am not sure what's the ignition but I am uploading pictures right now.

Did you see a spark ?

Not sure what you mean by the ignition. It's always "on" until you turn it off with the kill button.

When I was younger I'd just shock myself with the primary circuit, I could tell how much spark it had by how much it hurt. Not kidding.

On the US Spec 1976 Sprint, it had a round headlight and there was a key switch on the headset with a separate ignition cutoff on the handlebar that toggled rather than being a momentary kill switch.

This bike, on the other hand, is...something different...

Looks like a Bajaj CDI ignition, so it may have just crapped out. That, the trap headset, and lack of turn signals makes me curious about the provenance of this thing.

I had figured that the button/slider thing on the top right was for the turn signals. I don't remember it doing anything so I figured it just wasn't working

The kill switch circuit could be the problem

No, that's an aftermarket switch that usually goes with a 12V AC wiring harness. The three-position toggle on the bottom is for the lights: Off, brake/tail/pilot, and headlight. The small button is the kill switch and the larger button is the horn.

I think your bike is an overseas import that never had turn signals. Or the mounting holes were filled in when it was painted.

I have to find or go take a picture of the correct handlebar switch (they're unobtanium, no repop versions available), but here are a few pictures of my US Spec 1976 Sprint for comparison.

As in like the little button is stuck in the "pressed in" position according to the electronics so it's stuck off?

When he head it up and running 10 years ago we had to rebuild the carburetor and its just been sitting ever since

Pay attention to Chandlermans post, I said circut, meaning the kill switch system. He's zeroed in on the possibility of the switch being incorrect for the bike, meaning the harness and its apparatus device's

There are two scenarios at this point...

1) The Bajaj Ignition has given up the ghost and needs to be replaced. Even if that's not the immediate cause, it will be soon enough. They were terrible systems and you now have a proper option for a small cone electronic ignition with the SIP Vape. Put aside a few bucks in the piggy bank for when you're ready to face that reality

2) It's the kill switch. That's the green wire coming from the wiring harness into the CDI. Look in the junction box and you'll see it. Disconnect that so you can be sure it's not the issue.

I don't recall, but is this a new or old spark plug? The plug should be okay, even if it's been sitting for ten years, but I don't want to rule it out just the same.

You could try unplugging the green wire from the CDI and kicking it over...

Gotta know which is from the stator and which is from the harness, which is non-obvious since they're both run through the junction box in this case.

Good point

I always pull the one furthest to the right in the CDI - Or trace the solid green through the junction box, which always is the one on the right...

If the little kill button is stuck in, pry the cover off the switch.

Wondering if they didn't play with the junction box when playing with carb..

Kill button upper left

Just a though, but it might also be something simple like the spark plug wire is loose on one end or corroded inside after ten years of sitting.