Modern Vespa

So after a complete carb clean/rebuild my P died shortly after I put it on reserve? I filled the tank and put it back in the regular running position and every time I gave it throttle it died. After a bit of very slow ramping rev. I got it to return to normal.
Tank is clean.

I’m thinking it’s the rubber petcock disk?

Get a chunk of fuel line and a connector nipple, hook that to your fuel line where it usually connects to the banjo fitting and then do a fuel flow test into a can. You can pull your banjo and clean the filter screen inside while you're in there.

Do you mean clean the float bowl screen or the inside the tank filter?
Thanks

You're right, it's the screen on top of the float bowl. I've been dealing w/ all smallframes lately and theirs is under the banjo. If you cleaned it when you rebuilt the carb it should be clean, but if there is debris already, the problem is upstream and likely that rubber disk you mentioned disintegrating. Did you check your flow?

I've had my rubber disc come apart and block the flow to my carb before...on the way to a rally in fact...on the side of a VERY busy highway...right as the sun went down (at least it wasn't raining). It took about 30 minutes to diagnose down the problem...many because i didn't want to unload all of my camping gear and remove both the seat and tank.