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1966 Vespa 150 Super engine cuts out after 5 to 10mins

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Stewadan Avatar
Stewadan Dan Stewart
Brisbane, QLD, Australia   AUS
Hi,

I've got a 1966 Vespa 150 Super which was restored back in 2003.

It's my weekend ride and hasn't had a lot of regular running thanks to family life commitments. It started to develop this issue of running rough after about 5-10mins (spluttering) then eventually cutting out. As the bike become spluttery I was give it a little more throttle & revs which could buy you a few more minutes but eventually it would simply stop. Once stopped, it takes about 20mins before it will restart again.

I took it to a local Vespa guru last year (Pete Chmielewski at Silver Star in Wynnum QLD) to get it cleaned up & running sweetly again. Pete suspected the fuel was off and cleaned the tank / fuel system. He also fitted a new carburettor.

Despite this it keeps reoccurring.

I have also tried cleaning the fuel tank cap to ensure it is not creating a vacuum. I even tried running the bike with the cap open and it still cuts-out.

Non-vespa mechanically minded friends think it's an electrical issue however if I pull the plug out and earth it, it sparks beautifully (plug end looks perfect). It simply will not start for about 20mins (cooling down?).

To me it feels like it’s suddenly being starved of fuel.

Any ideas or guidance would be appreciated.

Thanks,
Dan

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itsraininginPDX Avatar
itsraininginPDX Matthew Hamm
Portland, OR, USA   USA
Hi Dan. I've had this happen on a p125. Not sure it's the same deal, but it was the spark plug for me. It would have good spark, but something would happen when it got warmed up. I swapped the plug and it was fine. It can really only be one of a few things though, fuel, air, or spark. If you hadn't changed out the carb, I'd say it was one of the jets. The holes in those are so small, it doesn't take much to clog them. Let me know if you track down the problem.

OlympiaScooterCompany Avatar
OlympiaScooterCompany Matthew Gatlin
Olympia, WA, USA   USA
When was the last time the motor was dropped and the seals were replaced?

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Stewadan Avatar
Stewadan Dan Stewart
Brisbane, QLD, Australia   AUS
2003 the bike was fully restored. It was stored between 2004-2008 (on blocks, fuel drained, motor wrapped etc).

Since 2009 it's had very in frequent riding (less than 500km per year).

Snozzelad-ss180 Craig E
St Austell, Cornwall, UK   GBR
Have you tried replacing the coil.? I had the same problem years ago and put a classic Vespa coil on and that solved it..

itsraininginPDX Avatar
itsraininginPDX Matthew Hamm
Portland, OR, USA   USA
Oh. That does seem the most logical next step.

caki Joe Caran
Sydney, NSW, Australia   AUS
Hi Dan, It sounds that you have an electrical problem.
Thing that can give you this kind of problems like: Points, Condenser, Coil or Spark Plug.
The reason I say that is because the engine stops after 10 minutes with some warning of splattering. To me this is a sign of an electrical component braking down as it worms up and it gets hot enough to completely fail.
When this electrical component or components cool down the component recovers its function and you can start your Vespa again.

Do this to confirm that you have an electrical fault not the fuel fault:
* Remove the engine cover and the air filter
* Have the can of "Start you Bastard". (this is an aerosol spray can with fuel in it)
* Run the engine and wait for the start of splattering
* spray the aerosol directly in the carby as the engine is running
* if the engine regains the normal idling speed or it starts increasing in revs it means you have the fuel starvation problem
* If the engine stops while you're spraying the aerosol, you have the electrical problem

Please let us know of the results so we can guide you further.

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