Modern Vespa

Ok another newb topic but I cleaned my fuel tap (couldn't replace because Gene at SctrsO identified is as an older model which has a smaller diameter than newer taps meaning to replace it I'd need to enlarge the hole in the tank).

Now I've put it all back together and the scoot started on first kick but died shortly afterwards. I'm thinking it started with the residual fuel in the pipe and once that finished it died. I then kicked it over for ages but no luck, it just sounds dry and no excessive smell of gas from the carb. (the gas tap was open on reserve)

I figure there's some air in the fuel hose that needs to work it's way through.. Is this correct or should fuel flow freely..?

Another thing... when kicking it over I noticed some drop of oil develop at the spline of the kickstart lever.. I figure this is transmission oil just working it's way through.. Way off or does this sound correct...? Maybe I have bad gasket somewhere...

thanks in advance!!

i wouldn't worry about air in the fuel line. fuel flows easily. sounds like something is blocked, or pinched, or something like that. probably the carb could use a cleaning/rebuild. the tiniest bit of debris or gunk can block a jet. sometimes even just liberally spraying carb cleaner in the jets and openings can help.

yeah, I left it overnight with the fuel tap open and this morning I could see residual fuel in the air box (new carb gasket required!). Still no start so I think I'll bite the bullet, get a new gasket and clean the carb at the same time. It'll be the first time for me..
It's strange that it started on the first kick before.. perhaps some dirt got in the fuel line while it was unattached.

Ok, thanks for the tips... I've replaced almost all the gaskets in the carb and cleaned the fuel tap but I've still got a problem... Here's my status..

* I put some gas mix in the tank above the normal gas inlet. Rode bike around with no problems but mainly on city streets so I was not opening the throttle fully in 3rd just because it was a bit stop and go. It seemed fine accelerating in 1st, 2nd, and 3rd no problem. Then after some time and maybe coincidentally along a stretch that involved full 3rd gear throttle the bike died. I looked in the gas tank and the level was still above the complete fuel valve. The bike starts back up ok... Then ride a bit more but it starts cutting out more and more until the point where it starts cutting out at every junction when it goes into neutral or the clutch pulled in. This happens on main valve as well as reserve. This is similar to the original problem I had which I pinned to a blocked reserve gas tap. So here's where I am with it..

* when the tank is removed but the tap still installed I can get free flowing gas in the normal position and the reserve position with no leaks when closed. This I'm happy with.
* yesterday I cleaned the jets and replaced carb gaskets
* when I rest the gas tank on the top of the bike with the fuel line attached and unscrew the carb fuel connection and then open the fuel tap I see a nice flow of gas both with reserve and normal tap positions.
* when I place the tank within the frame and do the same I do not see a nice flow of gas.

So roughly measuring the depth of the fuel tap from the top of the tank, and the distance between the carb fuel attachment and the top of the gas tank they appear about the same. I know that no fuel will flow naturally (under gravity) if the carb fuel attachment is at the same level as the fuel in the gas tank. This makes sense and can easily be seen by slightly lowering the carb fuel attachment and watching fuel flow and then lifting it slightly and it stops.

So after all the long winded description above my real question is should the gas be fed by gravity alone (which I suspect is true since no such thing a fuel pumps on a 1959 vba). I don't see how a carb is 'sucking' the fuel in.

If this is true it seems that my setup cannot be stock.. I've either got a newer tank which is deeper and thus fuel tap sits too low.

Can anyone either tell me I'm over-thinking this or does it sound correct..?

(it was a nice day here in NYC for test-riding!!)
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It sounds like your fuel hose is getting pinched or kinked when you put the fuel tank back in, which would account for the lack of fuel flow.

is the hose from the fuel tap facing the engine? when you replaced the fuel tap did you replace it in the same position? if you are getting fuel flow at all positions except when the fuel tank is installed then its gotta be the line somewhere.

I have an old fuel tap, not sure if it's original for this bike or not.. ('59 VBA). It points directly down.


http://picasaweb.google.com/noel.rycroft/VBAFuelValve#

I think my line must've been pinched as you suggest. I read a post on sbbs about how specific the fuel line length must be to avoid this.