Modern Vespa

Hi I have trouble with my vespa I was driving on the road suddenly started to lose power on the throttle and then stopped. I took the scooter to a garage the said ignition system was tested fuel pump and fuel system tested and ok and they change the injector as they found it faulty ..on my way back to home after a 15 miles ride I stopped for a drink and then the scooter didn't want to start have to wait around 30 min to then the engine cold down and the engine start again so in resume after a 20 minutes the engine get hot and do not start some people say its the coil and other people told me maybe the exhaust any help please

Non-starting when hot could be the coil or it could be the valves. When were the valves last adjusted?

According to the specs I found for a 2010 Vespa S 150, the engine has a carburetor so it does not have a fuel injector. Are you sure that's what the shop replaced?

I bought it few months ago I used some LIQUI MOLY Valve Clean but no changes i definitely will try to change the coil thank you for your reply 😊

Yes it's vespa 125 cc 2010 and the paper said they change the injector was not responding so they change it

"Valve cleaner" won't help if the valve clearance is out of adjustment. How many miles on the scooter?

You cannot correct an incorrectly set valve clearance with a cleaner...

I even doubt that such a cleaner can do anything.

That may be right. Could be some 125's were injected.

A Vespa 125 from 2010 losing power and stopping when hot is often due to fuel delivery issues, potentially caused by a faulty fuel pump, clogged fuel filter, or vapor lock. Other possibilities include a weak spark or an issue with the carburetor's idle jet.
Here's a more detailed breakdown:
1. Fuel System Issues:

Fuel Pump:
The fuel pump, especially in certain GTS models, is a common culprit for overheating and failing, leading to fuel starvation.

Fuel Filter:
A clogged fuel filter can restrict fuel flow, exacerbating the problem when the engine is hot and fuel demand increases.
Vapor Lock:
In hot weather, fuel can vaporize in the fuel lines, creating vapor bubbles that disrupt fuel flow. This is more likely with older fuel lines or if the fuel tank is positioned near hot engine components.

2. Ignition System Issues:

Spark Plug:
A weak or failing spark plug, especially when hot, can lead to misfires and a loss of power.
Coil:
The ignition coil could be failing when hot, resulting in a weak or inconsistent spark.
Loose Connections:
Check all electrical connections, especially those related to the ignition and fuel systems, as loose connections can be temperature sensitive.

3. Carburetor Issues:

Idle Jet:
The idle jet, which controls fuel flow at low speeds, can become clogged or worn, causing the engine to stall when it needs to idle.

Fuel Mixture:
If the fuel mixture is too lean (not enough fuel), the engine may run poorly when hot.

Troubleshooting Steps:

Check the fuel pump: If you suspect a fuel pump issue, have it tested or replaced, especially if it's a model with known issues.

Inspect the fuel filter: Replace the fuel filter to ensure adequate fuel flow.
Check the spark plug and coil: Ensure a strong spark by testing the spark plug and coil.
Examine the carburetor: Clean or replace the idle jet and adjust the fuel mixture if necessary.
Look for loose connections: Inspect all electrical connections, especially those related to the fuel and ignition systems.
Consider vapor lock: Ensure the fuel lines are not routed near hot engine components and that the fuel tank is not overheating.

By systematically checking these potential issues, you can pinpoint the cause of your Vespa's stalling problem and get it back on the road.

The scooter it's 8000 miles not much

I think I gonnavtry to adjust the valves and get a new coil cdi

Although it's possible it's the coil, suspect the fuel pump first. Fuel pumps around that year (2009-2010) had a recall for some models, so suspect this first, especially as the S125 only became fuel injected in 2009, so the pumps were not that well time tested.

You should hear the fuel pump 'whirr' when you first switch on. Next time you start from cold, listen for it so you'll recognise it next time. Next time it doesn't start when hot, turn off, turn on again and check for that sound. No 'whirr'=stuck fuel pump. Replace it.

Thanks everyone for your help 👍

The vacuum line to the fuel tap is worth checking too.

No fuel tap - it's fuel injected.