Modern Vespa

Hi gang, just a quick question about fuel lines. Before, i had used regular (black rubber)fuel line, i think it was 1/4" diameter @24" length. Now, when i got new line (1/4"), i noticed the rubber was alot stiffer, and had a hard time getting it on the fuel taps. I noticed it stated it was "fuel injection line".
Is this okay to use for 2-stroke application?
When i cleaned the jets on the carb tonight, I noticed a little black residue on the bottom of the jets, maybe seepage from the rubber?
I believe 1/4" diameter is the right one, correct?

If you got it on and it's the right length, it'll be fine. It's just pressure rated, but will work the same for non-pressurized applications, it's just more flex and stretch resistant, as you already know.

Chandlerman... ok thanks. It was stiff as all heck. I was worried when i noticed some black residue on jets...i thought it was some of the rubber material was running off?

5/16/8mm ethanol friendly hose is easier to work with.

I'd clean that carb with an ultrasonic cleaner and compressed air.
That residue will also be in the important channels in the carb.

Is it 1/4" line to use or 5/16"? Wasn't originally line size 7mm??

Just looked in my spare parts bin, found a spare section of new, fuel line like i used before. You can see the difference in the pic.. 5/16" on the right.
Could it be that the bike is getting a bit of fuel "starvation " with the 1/4" line, or it will would okay?

You'll be fine on a 6mm/1/4" line.

For comparison, half the fuel line on my Lammy is 6mm (1/4") line, and that's feeding a 34mm carb and a 210cc cylinder top end.

8mm is really preferred, I think, but mostly because it'll fit the fittings than any real need, IMO.

Chandle....
Thanks. Was worried about the possibility with "fuel starvation " with the 6mm line.
On the flip side... with the 8mm line, if hitting WOT, could there be a slight overflow of gas going into the carb, or will the needle/float be able to control that?

Original Vespa line is 7mm. If reasonably stock anything that fits will work.

If the float and needle are working correctly, they will manage the flow for you.

If you think about the chokepoints in the fuel flow, the first one to consider is your main jet. It's somewhere in the neighborhood of 1.2mm (120 main). Upstream of it is the float passage. It's only 1.25mm unless you've drilled it out. Upstream of that is the float seat, which is only a couple millimeters, too.

And since area scales geometrically with radius (Pi*r^2, y'know), 6mm is 28mm^2 versus 1.1mm^2, so 25 times the area from the fuel line to the jet.

Okay, so i guess i should be good with the 6mm line...
thanks