Modern Vespa

Hi!

I inherited an old ET2 from a mate a while ago and have been trying to get it running recently. It's been stood in his work car park for a few years!

I replaced the battery and spark plug, cleaned the float chamber of the carb and tried it - nothing. Decided the fuel tap was broken so replaced that and hurrah - it starts!

BUT, it only runs for about 5 seconds before it dies, plus it dies immediately if I try to rev it up. I fiddled on with the idle screw and it didn't seem to make much difference. However, if I detach the auto choke and sort of half leave it in I can rev it up.

Does that mean the choke is faulty or am I actually getting around some other problem by pulling the choke out a bit? Is there a really easy way to check if the choke is working?

The plug is blackened and dry which makes me think it's not getting enough fuel but then why does it die when I try and give it some gas from the throttle?

Any help much appreciated!!

Anybody? Reluctant to buy a new choke unit if that's not the problem.

Starting to think it might be gummed up carb needles - do I need a carb rebuild kit to service it or can I just put it all back together (gaskets etc) reusing the old parts?

Cheers,

Chris

The throttle actually doesn't give it gas. The vacuum from the engine turning over both opens the fuel tap and draws gas into the cylinder.

If your plug is dry, the tap may not be functioning or the jets in the carb may clogged. Since you replaced the tap, it's probably at the level of the carb. However, like I said, the tap is opened by a vacuum. If the vacuum hose is cracked or loose then your shiny new tap might only partially open or somesuch. To test, disconnect the fuel hose from the tap, and turn the engine over. A nice dribble of gas should come out while the engine is turning.

Once you know that gas is flowing freely at the level of the tap, I'd recommend inspecting the fuel line for obstruction.

If the fuel line is good, buy a carb rebuild kit (cheap) and replace the jets and gaskets and needle.

Now that engine should be getting gas. Make sure the fuel/air mixture screw is set appropriately (it's critical - the idle only adjusts the tickover rate).

There is a way to test the choke, I believe, but I don't know it. A search on the site should turn up the answer if it is there. However, depending on how pricey the choke is, if the scoot still won't run for more than 5 s after the above changes, I'd be tempted to just bite the bullet and buy it.

Keep us posted!

Thanks for the pointers - i think I'll give the carb a rebuild anyway as it probably is a bit gunked up. The confusing bit is that when I detach the electric choke and then half push it into the position it fits in I can rev it up (i.e. the engine must be getting gas!).

Yes, for what it is worth I do suspect you need a new choke. But I figured it's best to check the cheap stuff first and be methodical about it

That's a very sensible approach! Thanks for your advice

Just a random question. What the heck does a rebuild kit for such a small simple carb like ours consist of? A float bowl gasket? I've rebuilt my carb a bunch of times and never seen anything worth replacing for except for that gasket.

You're right, they probably don't sell "kits" for this at all - I was thinking float needle and gasket, and a good cleaning of the jets when I suggested rebuild.

Curiously I am having a similar problem after returning from repair shop. Since the repair shop is 45 minutes away I thought I'd run it by you guys. Carburetor is rebuilt, choke is brand new, it ran for 10 miles after I got it back from the shop. Where do I start?

This thing will start in the morning, run for about 10 seconds, then go ito a low idle and inevitably stop. Once it does this it won't start again for some time.

Update: I got this thing running yesterday. Got past the 10-15 second idle then die period. Ran it around a bit and it runs fine...once you get it going. This morning, right back to 10 seconds and then done.

Any thoughts?

You say you are having similar issue to the OP, but we don't know what tests you have done or what other symptoms you have.

1) run it until it dies, then check the plug. Is the plug dry?

2) run it until it dies and then check for spark (it's conceivable that you have a faulty cdi which ceases to spark when it warms up - many ET2 owners have had their CDIs go bad, although I haven't seen this type of case yet if your CDI is to blame)

3) Just to check, there IS a way to test the auto choke (I know you said it was new, but dying after warmup does sound suspicious). Try a search to see if it pops up.

4) The carb was rebuilt - what about the hoses? Check for cracked vacuum hose and deteriorating fuel line.

Let us know!