Modern Vespa

G'day guys, new to forum. Need some help.

So it's a weird problem. When I ride my vespa I can get around 2-3 km before the engine will just cut out. And then, all I have to do is open the fuel tank and it'll start straight away and run for another 2-3km before I have to do it again.
It's almost like there's not enough air getting into the fuel, but I've adjusted the mixture screw and it has only had a small effect. So I'm thinking it's got something to do with the tank and connection.

Hope someone out there has any ideas and could help me out. Would be much appreciated.

Thanks.

May be that the fuel cap breather is blocked. Leave it loose and test ride.
If that's ok then undo the banjo at the carb and check for constant flow... the hose may be pinched or kinked.

If it turns out the breather is suspect look for the tiny holes in the cap. Stick a pin or piece of wire in there to clear.

yuuuuuuup

you can either rebuild and open up the gas cap vent holes
or
use some compressed air and blow it out

there is metal filter material within the gas cap that gets clogged up over the years. If you rebuild it do it away from the gas tank and be careful about getting the drill bit wrapped up in the filter material.

easy fix

I have this issue often in my scooters, it is typically the fuel tap having hard time getting fuel from the on or the reserve position. It only last for a moment and it goes away the moment I turn the fuel tap to the proper position.

Thanks guys.

Yea the fuel cap was all blocked up. Cleaned and all good now.

Cheers
Jack