Modern Vespa

hello everybody
I just got a vespa pk50xl from 1991 with a new carb cilinder and exhaust. The problem is I can't get to get the bike to respond fast to the gas. When I hit the gas it takes 3 seconds before the engine starts to really rev up. it is also hard to let the bike run stationary. I played already with the stationary screw but didnt help. I also checked if all jets were clear in carb. I put a video to make it clear for you guys. I also have a question about the screws on the dell orto carb. 1 is for stationary but what are 2 and 3 for (see picture ) the setup of the carb is a dell orto 16 15 with 65 for main jet and 50 for small jet.

https://youtube.com/shorts/XSA_XA2GQSk?si=qWhBWX5VCaIarCcf[/url]

If it's problems with revving, idling and starting, the mixture of air to fuel is probably wrong. Screw number 3 adjusts this, I can't remember which way turning it does which, I would advise trying experimenting, screwing it one way will make it so the revs never come down and screwing it the other way will make the revs drop down very quickly and possibly below idle after revving. If you screw it all the way in then turn it out by 1 and 1/2 that should be about right and you can tinker it from there! I can explain how it all works in more detail if you would like!

Thanks for the info! Do you know what screw 2 is for? I set it now also 1,5 screws out but I do t really know what its for

What cylinder and exhaust?

Number 1 is idle screw.

Number 2 isn't a screw. It is idle jet. It must be screwed all way in. What size is it? It marked on the side.

Number 3 is mixture screw. When you screw it out the mixture becomes richer. For starting point screw it full in and then screw for 1.5 turns out. If you talking about jet in the float chamber - it is choke jet and you don't need to change it, left it as is.

Idle jet is 42

it is just a normal 50cc and a sito exhaust which looks like the stock exhaust

Try 38 idle jet.
And main jet in range of 55-60.

Original jetting with 16.10 carb is:
38 idle jet
53 main jet

You also can try to take off air filter and look how it change acceleration.

Okay, I will try the 38 idle screw, do you know where I could buy this? Also im gonna start with just the idle screw because in high rpms the engine runs good and response fast so I think main jet could be good, the spark plug is also a good Brown color.

Sip Scootershop or Scooter Center.
I prefer SIP.

Idle jet 38
Main jet 60

And don't buy these long type idle jets - them tend to block with dirt often in long nose. Short will work without any problems.

Okay thank you very much for your reply!
-Off topic but do you know how to connect the shifting? I cant find what piece brings the 2 pieces I marked on the picture together. I have a 1991 model with 1 shifting cable.

It is PK XL2 model. It bit hard to find correct cable nipple. It bigger that on other Vespas with two gear cables.

Some time ago I saw it on SIP but now can't find.

I think something of this will work:
One
Two

Okay perfect, thank you very much!!

Good luck with repair!