Vespa Ciao backfiring / not running

Hi all,

After my stolen moped was returned to me this spring, I decided it could use some TLC. After being driven by whoever took it last year, there were some serious issues that needed fixing badly.

Amongst these issues was the fact that shortly after getting it back, it became harder and harder to get it running up to the point where it just cut out entirely. I tried replacing a few parts, but to no avail. At this point, taking apart, cleaning and rebuilding the engine didn't seem like a bad idea since I wasn't going to get it running like that anyway.

Now that I've put everything back together, the Ciao still won't run. Even worse: It occasionally fires out of both sides (intake/exhaust) when trying to start it. With the choke in, or at low throttle the engine doesn't pick up at all. At higher throttle, I can hear something happening, but there isn't nearly enough power to keep it running stationary. This is also where the detonations occur.

What I've replaced and tried so far (in no particular order):

- Replaced ignition stator (coils behind the flywheel)

- Replaced CDI (Coilpack thing on the side of the frame)

- Replaced all engine gaskets

- Exchanged spark plugs with a working Ciao engine

- Exchanged carburetors with a working Ciao engine

NOTE: I tried both Ciao's after exchanging parts. The previously working one still worked after switching parts, the broken one still didn't.

- Took apart and cleaned the engine internals thoroughly. Removed carbon deposits, built up gunk, dust, oil, etc.

- Checked cylinder head: decompression valve and spark plug seal properly

- Checked cylinder/piston assembly: rings seal properly

- Checked petcock: provides more than adequate flow of fuel

- Checked ignition by holding the spark plug to the frame: seems to work fine outside of the engine.

- Tried to run it without air filter: no change

- Tried to run it without exhaust: no change

I'm at a loss here. Any ideas on what my next attempt at fixing this issue should be are more than welcome at this point. Thanks in advance!

DSC_0093.JPG

Re: Vespa Ciao backfiring / not running

Timing . ;)

Re: Vespa Ciao backfiring / not running

How would that work? I can't adjust the timing as is possible with the older type Ciao's.

Picture below is the stator used in my engine. It can only be mounted in one way. Also, the flywheel doesn't have the 'window' that allows for adjustment of the contacts. (edited)

stator-allumage-1tek-origine-piaggio-50-ciao-12v.jpg

Re: Vespa Ciao backfiring / not running

look up timing a cdi in the wiki, you'll need a timing light some time to digest it, then lap the crank taper and toss that woodruff key.

Re: Vespa Ciao backfiring / not running

Thanks! I'll look into the wiki then.

What still bothers me is how it would be possible that the engine is off timing while the system is set up to only go in one way. If this really is what's wrong, how'd it happen?

Re: Vespa Ciao backfiring / not running

Changed timing as per the Wiki, problem solved. Much appreciated!

Re: Vespa Ciao backfiring / not running

Dirty30 Dillon /

Literally never had an issue with Vespa CDI timing being perfect. If it's anything but a Wild build, it should be fine on the stock key position.

Also, seems to me like you either had no key in there, or the key slipped the way. Very classic symptoms.

Re: Vespa Ciao backfiring / not running

I like the mags on it.

Re: Vespa Ciao backfiring / not running

damn! 5 star mags on my dream list!

Re: Vespa Ciao backfiring / not running

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> Literally never had an issue with Vespa CDI timing being perfect. If

> it's anything but a Wild build, it should be fine on the stock key

> position.

>

> Also, seems to me like you either had no key in there, or the key

> slipped the way. Very classic symptoms.

this

also check that your crank seal is good, i did not see you mention this.

also make sure your piston is not upside down

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