Modern Vespa

I have a U.S. model 1967 Vespa SS180 that is giving me trouble. The motor has been rebuilt, I have cleaned and rebuilt the carburetor recently, cleaned the gas tank and added a fast flow fuel tap. I added a Pinasco Flytech ignition system as well. My problem is the power starts cutting out, backfires, and eventually stops all together (very hard to restart right away) after I have been running it for some time. I had this problem with the stock exhaust and now with the SIP Road 2 I added, and yes, I did rejet for this exhaust.

The SS starts up easily and runs great for awhile, but once it gets going (sometimes for an hour or so, and sometimes not so long) this problem resurfaces. If anyone has any ideas, please share them with me. I am ready to push this thing into the ocean (not really).

My only guess at this point, as the motor runs fine when it starts, and there is not a fuel issue, it has to be spark related. I am thinking I need to replace the CDI even though the Flytech kit doesn't have that many miles on it.

Thoughts?

I would replace the CDI with the BGM version; static timing.

https://www.scooter-center.com/en/cdi-bgm-pro-with-fixed-timing-for-idm-ignition-type-ducati-blue-vespa-px-pk-lambretta-used-for-polini-idm-vespatronic-vespower-varitronic-flytech-parmakit-bgm6697?number=BGM6697

Hmmm.

I am chasing a similar issue on my Rally 180 engine.

Speculations from the cognoscenti are a loose wire grounding out somewhere intermittently... or the flytech shitting the bed.

I'll circle back as my investigations progress.

I suggested the stator might be bad to Andreas Nagy, as he is a Pinasco dealer and the one that sold me the kit. He said he has never heard of a bad stator. I then suggested it could be the CDI, and again he said they don't usually go out that quickly. I just want to figure this out before I just roll the SS off a cliff.

The SS has the stock wiring, just as my GS160 does that is also running this same setup. The SS runs like crap but my GS runs amazingly. What the heck?!

Do you like this CDI better than the Pinasco one? I love the performance of my GS160, which also has the Flytech kit, but my SS is just trouble. My wife hates this scooter, and that's not good. It is so bad, that the only thing reliable about the SS is that it will let us down.

You could always do a quick Swap the cdi off your GS onto the SS and see if the issue goes away.

I have been hesitant to mess with my GS, as it runs so well, but there should be no harm in doing a switch just to see what happens. At least I will know if it is the CDI. If not, then I have to dig into the wiring loom as I can't see what else could be the problem (I don't really want to dig into the loom).

You can push it into my garage instead 😅
Have you performed a leak down test ?
I would suggest as the others to change your CDI.

+1 on looking at the CDI first… sounds like a bad ground.