Modern Vespa

Man, my scoot just doesn't like riding two up. Took a short ride yesterday with a passenger and the scoot wasn't happy. She started bogging down when accelerating and plain didn't want to run great above idle. I thought I may have fouled the plug so I replaced it but that didn't help. I noticed under the old spark plug a thick black oily substance. I'm not sure if that was there before this happened. Hmmmmmm. I'm off to tinker with it. I'll save the two up for when I get a modern. Thoughts? - Todd

Does it only do that 2-up?

If so, is there a fuel line running under the pillion's seat?

LAst time it did this it was the idle screw backing out but that isn't the case this time. The fuel line stays inside the frame, aways the the seats at all times.-Todd

Hmm, After poking around I DO infact think it has something to do with the idle screw. Even after screwing it all the way in the engine does not seem to be idling as high as it should. Also, If i remove the screw and put it back in the problem seems to go away only to return a few seconds after driving it.
Time for a carb tear down!
I <3 vintage