Modern Vespa

I am having a nightmare of a time with fuel starvation on this scoot. I have taken the fuel tap apart, have changed out the fuel lines and installed a filter, rebuilt the carb a half dozen times, and I have confirmed the fuel cap vent works. I have had times when it runs great and I can ride around the block and then I will end up in a situation where i'll have to kick it 30 times, and then it will rip to life, run for 20 seconds and then die again.

The only idea I have is that I shouldn't be using the spring loaded float needle but that doesn't completely make sense to me unless my fuel consumption is high enough that fuel flow won't keep up.

Is it possible that the early VBA fuel tap is just not free flowing enough? That doesn't really explain why it does/doesn't run sometimes. I'm mildly concerned that the way that the fuel tap exits the tank (straight down) that i'm kinking the fuel line and restricting the flow.

Thoughts? I'm at wits end.

H

I'd think anytime you put a kit on it you'd need a fast flow tap.

That'd definitely help it I think, also you may need to drill out the float bowl passage. A better more knowledgeable person could confirm or deny that though.

You should certainly have enough flow to ride around the block. CDI ???

What kind of filter and where exactly?

Its a tiny fuel filter just below the fuel tap outlet. Its the K&N bronze filter for a 1/4" fuel line that looks like a cone.

I think my fuel line is kinked, i am going to try to look in through the bellows opening with a mirror.

H[/url]

Ditch the filter.

Agreed. There is already two other fuel filters on this bike. If you can't get the fuel clean with two, it ain't going to be done with three.

If the fuel tap and carb are healthy, then the OP most likely has bad routing on the fuel line.

for the Pinasco 177, the original VBA fuel tap is more than plenty. . .as long as the tap is healthy and clean. You do not need a fast flow fuel tap.

What is your current fuel hose? Use American made rubber fuel hose at 24" length would be my recommendation.

I was working off a 19-20" fuel hose length. That note came off the wall in the shop where I have my bikes. I will get some back rubber fuel hose, 24". That may stop the kink.

h

It's possible that you are pullng a tight bend at the tap with a short hose.

Just thinking... if a bike gets 40 mpg and it takes 40 minutes to travel 40 miles at 60 mph then the fuel needs to flow a gallon in 40 minutes. The hose should drain that much out of the tank into jug a lot faster than that.

Can you measure the fuel flow? How long does it take to fill a quart jar? If less than 10 minutes or so, its not a pre-carb fuel flow issue.

FYI, My old Honda sensei always used to say "3/4 of all carburetor problems are electrical."

Yes, this sounds very similar to the problems I had with a bad coil on the SS.

I set this up to help you out on how to test flow easier w/ less mess, and I wind up discovering a potential problem that I had no idea was lurking. So thanks, Hal!

Well, that will do it.

So you think all that rust settled to the low spot in the fuel line and just sat there? Maybe at some point it builds up enough to restrict flow?

I know my the petcock on my large frame has a sediment bowl and my small frame does not. Good idea for periodic maintenance. Thanks.