Modern Vespa

Hi Guys.

Picking your brilliant minds again...

The pic you see shows the fuel leak in question, after a mere 1 hour! So that's pretty major I'd say (believe me, it's pretty large after leaving the scoot for a night). The leak shows right under the gear box, as you can see. Notably, the engine won't start until 10/12 foot kicks (or with the electric starter for quite a while) and it exhibits a large amount a white smoke for a while - I would assume these issues are related with the leak, but you'd know better.

The fuel tap is completely ineffective (putting the lever in the shut or open position doesn't make a difference) so I am changing that (together with the fuel hose) next week-end with a guy who knows what he's doing. Since we are removing the fuel tank, I'd like to take the opportunity to address multiple issues and I was wondering whether you guys had suggestion as to what additional issue to look for and, IN PARTICULAR, whether I should buy some parts in advance of my repair - like say, gaskets, bolts, sealant, etc. replace the oil gasket, dispenser, etc. (I also have an oil leak but it's far less).

Thanks for the help.

Take a look at your carb first. I think you might have something loose there and now you have fuel coming out of your carb box. That is the first thing I would check looking at your photo.

Thanks. Like what/where?

Probably the rubber grommet in the fuel tap. Easy to replace. Replace the fuel hose whilst you have the tank out. They tend to become brittle and split. Replace it with a proper black rubber fuel hose.

I agree with both of these observations/sugestions.
Fuel is getting passed the fuel tap washer and the carb float valve. Check the the carb box for fuel. If you find it puddling in the bottom or the carb body looks wet; start with the float needle. If it's all dry and still leaking, look under the body infront of the motor. If you find fuel it's likely coming from the tap. If both are wet then both may be leaking. I've known people who never turn their fuel tap off and never had a leak (I don't recomend that) and thats what the the float needle does; keeps the gas in the carb until it's called for.

I had a similar issue. In my case I had both a faulty fueltap and issues with my float/needle in the carb. I replaced both and have been good for years. As stated above, trace the leak to its source to help determine issue.

Great, thanks guys.

Yeah, I have a new fuel tap and will work on it this weekend.

Regarding the float needle, do you mean this one?:

Float Needle Valve DELL`ORTO
for PHB carburettor
incl. float needle Ø 4,5mm and
gasket

If so, I see they come as 150, 200, and 225. Which one should I get?

Also, I note there is yet another one with a larger diameter of 5.2mm in the sizes 200-400.

Which is the recommended one?

That being said, the carburetor does not seem to be filled with fuel, so this float needle replacement may be an unnecessary.