Modern Vespa

Greetings everyone.

I have a P200 that used to run like a champ, then I (stupidly) let it sit for over a year while I remodeled my basement.

I pulled out the gas tank and cleaned it out, and also rebuilt the carb (with help from a friend).

Now I can get it to start, and it will idle just fine indefinitely. However, it chokes out and dies about 10 seconds after I take off.

I can then restart it just fine, and it will idle no problem again, but as soon as I take off the same thing happens.

If I rev it high while in neutral it also dies off after several seconds.

When it dies, it sounds like it has when I've run out of gas in the past, so I'm thinking that the problem is with the fuel getting through somehow.

I asked around a bit, and most of the suggestions were to check and clean the main jet, which I did when I had the carb open.

Any other suggestions? I'm at a loss and it's killing me to see it sit in my garage.

Thanks much everyone.

--Casey

the bike is toast, yo. i can take it off your hands for 50 bucks.

if nothing changed with the bike since you last ran it, i'm hard pressed to think it's anything OTHER than your carburator/jets. first question, though...why did you clean the tank? with what did you clean it? first thought is main jet, and that is likely the case, but it's also possible that the fuel tap is clogged up and allowing just enough fuel in to run at idle, and not enough for the main jet to do its job (if it is in fact clean).

Your idle and air/fuel mixture screws may need some fine tuning, especially if you removed them when cleaning the carb. Have you checked the fuel line for kinks?

Check your choke cable is working properly. You may be able to push/pull on the choke but it may not be working on the carb end.

Sticky float/float needle
Take the carb appart again and clean not just the jets but all the passages in the carb with compressed air.
If it sat with gas in the carb, the float needle will get gummy and you could have fuel slime clogging up the passages in the carb.

sean s

I'm going to second the sticky float/needle suggestion. Sounds like a fuel flow issue. If that doesn't solve it, you might want to check fuel flow through your fuel tap and hose. You might also see if the vent in your gas cap is clogged. You can check that by running the bike with the gas cap open or loose. You can check flow by pulling the fuel hose off the carb a little, and turning on the fuel tap. There should be a at least a slow trickle.

So what did you find?

I'm sure you've solved this problem by now, but just to add my own experience for posterity...

I had this problem too after rebuilding my P200 a few months ago. The problem was the fuel line being pinched when I set the tank back in. Enough fuel flows through to idle, but when you rev the engine it drains out the line faster than it fells. I cleaned all my jets and adjusted everything before I thought to pull the tank back out and set it in more carefully.