Modern Vespa

Hi Guys, please forgive me for posting here, but I could not find a good forum for Aprilia, so since my Aprilia has the same 50cc 4T drivetrain, I have decided to post here.
So if you know a better place to post it, please let me know.
My 2008 Scarabeo 50 has a very strange problem. It starts fine when engine is cold. Runs for 10 seconds and dies. Then it refuses to start, unless you crank for a very long time. Then it can repeat the cycle and eventually starts and runs. When it warms up it, it runs amazingly. Restarts fine as well.

I have taken apart the carb and cleaned it in ultrasonic bath, pushed the wire through all the passages. Did not help.
It feels like it gets too much fuel and floods.
Any ideas?

Your Aprilia should have an accelerator pump on the carburetor. After it dies, try rolling the throttle open twice, then attempt restart. If it fires, even briefly, then it's likely not too much fuel.

My money is on your pilot circuit. You may try cleaning the pilot jet with a guitar string; Ernie Ball #10 works for me.

When you disassembled the carburetor, did you find the washer and O-ring on the low speed adjustment screw?

When you pulled the low speed adjustment screw, did you turn it in first to the stop to determine the original setting before removing it? If not, try setting in between 1.5 and two turn out from fully seated as a baseline setting

AZ, thank you for your reply. I have tried rolling the throttle and it did not help.

I have just realized that I did not pull the low speed adjustment screw.

Will pull the carb tonight again. Will report back

UPDATE.
I have went again and figured out that if I pump the accelerator 6-8times it fires up!!!
So it Is low fuel issue.
Do you think it is pilot jet still?

I would still give the pilot circuit a good cleaning. Pull the jet and hold it lengthwise up to a light. You should see a small pinprick of light through it, about .2mm in diameter.

If needed, shoot some carb cleaner through it lengthwise, feeding through the slotted end. You should get a fine, focused spray out the other end, with smaller, more diffused spray coming through the atomizer holes in the sides.

Ok, I feel dumb, but where is the idle adjustment screw? I see this Wierd looking brass screw, which I suspect is a mixture screw.
On the side note, the gas that is the tank is of this strange yellow colour. It smells fine, but who knows. Good gas is on the left, tank one is on right (the sediment was just some dirt I had in cups.) I am draining the tank now to fill it in with fresh gas just in case.

Mixture screw is the little brass screw, near the intake manifold of the carb.


Photo credit to Scooter West.

Is that what ou meant by low speed adjustment screw? I am used to 2 screws, idle and mixture.

So on my picture it needs some strange shaped socket. Grrrrr.

The D tool is available on eBay on Amazon. It stinks that it needs a special tool, but it's quite findable.

Idle screw is the one that rests against the throttle cable pulley, visible in your third picture.

Or you can bend in one side of an appropriate cartridge. i think .22 will work.

Hi guys. Thank you for all the help. Do not want to be overly optimistic, but I think she is running fine.
Took the carb apart, used the wire on the primary jet and on the main one. Pulled out the mixing screw and blew it all. Set the mixing screw to 2.5 (it was set to 2)
Drained the tank.
To be honest, I think that the old gas was the problem. It did not smell bad and previous owner said he always used stabilizer, but that yellow colour was not good.
Took it for a little drive around the block and she runs much happier.

She tops at around 45-47km/h. Does that sound right?

Also I noticed that at wot she tends to have little jerks, like she is hitting the rev limiter. What do you guys think?

By the way, this is my first Italian scooter ( had a bunch of Chinese bikes before) and now I feel like wasted lots of time. This Italian baby is fantastic!

It sounds about right for a 50cc. The coil/CDI is internally governing on these machines. I've read of a trick for de-restricting them by discretely cutting the CDI casing to derestrict it. Conversely, ScooterPartsCo sells a de-restricted coil/CDI.

Need more, look into Malossi's 2V 80cc kit with the cam.