idling/stalling issues

I've got a 1977 Vespa Ciao- i just bought it maybe two months ago. it's my first moped. from the outset, it's had some problems starting without giving the throttle some gas to get it going, and some real problems idling before being warmed up. in addition, it has the nasty habit of dying at red lights. when it's running, it runs fine.

i brought it back to the guy who sold it to me, since he was nice enough to offer some service on the bike. we took apart the carb and cleaned it, changed sparkplugs, adjusted the idle, etc, and it seemed to be doing ok. as soon as i got it home, it was up to the same old behavior again. any tips/ideas/directions as to what might be the culprit?

thanks much,

sean

Re: idling/stalling issues

Idle should be set only on a hot engine ..

Take it for a reasonably long ride, come to a stop, and immediately set idle speed (and idle air:fuel mixture if there's an adjustment for that). If idle was set properly but it won't idle when hot or when cold, it's something else.

You want a clean carb, clean, tight air-intake system, no vacuum leaks, no fuel leaks etc .. The float level has something to do with idle.. Starting and idling require a lot of gasoline.. a rich mixture. The choke helps richen the mix by cutting off air intake. Adjust choke cables and/or mechanisms as is applicable.. be sure the choke is working correctly.

And the entire fuel pathway from tank to engine should be clean including filters .. Many times, a bike that has been sitting around collects lots of junk.. rust and deteriortated gasoline.. and will continually get the carb dirty again until the source of that junk is eliminated.

Re: idling/stalling issues

Your mechanic may have missed cleaning the Idle jet in the carb casing. It is easy to miss. See attached pic. Carb cleaner alone won't clean it, you have to use a pin or very tihin wire to clean it out.

Also check or replace your tail/brake light bulb. It is a dual filamet bulb and if the brake light filament is burned out, you will kill the engine each time you apply the brakes (like at a stop light) The bike will restart just fine but will die again at the next stop sign when you apply the brakes.

Bulb is a GE 1154

1122533356_dell_orto_carb_idle_jet.jpg

Re: idling/stalling issues

Thanks much for the advice...with regards to the brake light-it's functioning, so are you basically saying that there are two filaments, and that one burned out filament alone could be an issue?

also, the idle jet-is that the same little pin hole that the fuel passes through?...because that was given a thourough cleaning with a thin wire.

i realize that at this point i know very little about engines, and mechanics in general.

thanks,

sean

Re: idling/stalling issues

thanks for taking the time to give some advice...i'm pretty sure the choke is okay. it physically functions fine-as in, it stays in a locked position when put into place, and doesn't release until the throttle is applied.

the filters were cleaned, but your point about the carb possibly being perpetually clogged by dirt from the tank seems to fit with what's been hapenning.

thanks again,

sean

Re: idling/stalling issues

The bulb is a dual filament, one filament for the brake light circuit and one for the running light (tail light). One filament can burn out and the other still be good.

Put the moped on the center stand with the engine running. Apply the brakes and look to see if the Brake light comes on in additional to the running light being on. If both lights don't come on and the engine dies, simply replace the bulb and see if it solves the problem. The tail light is also grounded under the fender so make sure that ground is tight and not rusted or corroded.

There are two jets you can run a thin wire through, one is the main jet which is a brass screw. Did you clean out the hole in the brass screw AND the one in the picture I posted (Idle Jet)?

Re: idling/stalling issues

so, i'm not sure if the idle jet got cleaned...i'll open it up myself and have a look around.

with regards to the tail light, i tested it out when i got home from work, and it didn't look like a second light went on when i applied the brakes. when i had the bike up on the stand and was running the motor to get the bike warmed up, fully applying the brakes even dimmed the light a bit. not sure if that's at all normal. i'm going to go ahead and put in a new bulb, and see if that helps. thanks again for the tip.

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