Modern Vespa

My restored (2 years) 1972 Vespa Sprint stalls out going uphill. Starts up on the 3rd kick every time, idles fine and revs fine. When I pull out the choke the bike then runs fine up the hill back to my home in hilly San Francisco. I put out both of the jets, cleaned them out but didn't make any difference. That's all I'vd done so far. Any suggestions on why this is happening is greatly appreciated.

It was running fine prior to the recent 2 months of much needed rain in the Bay Area.

Is there anything that could be pinching a pipe or wire when all the weights loaded towards the back like going up hill ?

Is all the fuel system correct, running of fuel pipe so on as to not hinder flow when the angle shifts, ie pipe too long & low so no gravity feed?

Get a few big matescreen or some wood/straps etc & truse to recreate the angle so you can have a nose

Slow fuel flow

Are you saying that you are running the scoot on choke up the hills?

i would try a new fuel tap.

Yes, it stalls going uphill, I quickly pull out the choke (instinctfully) and the engine came to life-made it up the hill to the garage.

Float level is wrong?

You brought a Sprint, not the Pikes Peak version?

Resolve this problem by leaving the choke out about 1/8" from closed position. Not sure why but it works and runs fine. The choke has to move from fully open until the engine warms to the 1/8" position. Pulling the choke out to 1/8" from closed position won't work.

Well... that's not really a resolution. The scoot wasn't intended to be run with the choke even partially out.

My money's on fuel line's either a couple of inches too long or it's not routed around the tank correctly. Should be a simple fix, might as well just do it.

Rode the Sprint into Scooter Center, SF with the choke half way out. Confirm by them that there's a bad air leak with the engine. Need to have the engine go through a 100% tear down and replace all seals, etc. Will post update.