Modern Vespa

My Sprint starts fairly easy, runs well for a few 100m, then dies as if it is out of fuel. If I run-start it again, it starts fairly quick, but dies again in a few 100m. At that stage it does not kickstart at all.

Enough fuel, spark is good, fuel cap breather open. I have tried a slave condenser, still no joy.

What else can I check or try?

Dont know Sprints, but I'm guessing electrical. If you let everything sit for a while can you magically kickstart it? Then it dies when the motor gets warm? Then if you let it sit for a while it magically works again? Thats definitely a failing coil.

If not, is there a kill wire on those? Disconnect it or the handlebar cover and ride. Maybe you have something similar to the P200's green wire of death (kill wire sucks and shorts on you).

It sounds like your fuel line may be kinked, allowing enough fuel to reach the carburetor to start and run until the float bowl runs dry, then slowly refilling. I would pull the tank and check the fuel line before doing anything else. A bend in a fuel line can become a partial obstruction over time.

when you pull the tank like apex says, get a fuel flow measurement with cap on and cap off. this way you can check your fuel tap and your venting. take the time to flow 1 pint. you want nothing more than 30s.

I'm betting on gas. Here's how to test so you can eliminate spark.

I had a similar problem w/ my Rally - couldn't be sure if it was gas or spark when it died. So I added a 2nd external sparkplug to see if spark died when the motor did. Yep on mine, there would be spark then suddenly zero spark. Fixed the ignition and scoot ran good after. Here's a link w/ a vid and a pic of how to do it.

https://modernvespa.com/forum/post1548781#1548781



Assuming you have a good plug in the motor, you should get a spark on BOTH plugs & your motor will run if you're getting gas etc.

Sure sounds like fuel, or rather, the lack of.