Modern Vespa

Hi,

So the story is I added a 75cc polini to a good running PK50XL engine. Change the manifold and carburettor with a 16.16f. After that the problems started.
We had after warming up always a high idle which I could not get rid of. I suspected the connectiion between carb and manifold.

But to be sure we pulled the engine for a compleet overhaul to start fresh. But the problem stayed.

Not satisfied by the some what loose and short connection of the 16.16 on the manifold I decided to by a SIP DSPC 17.5 that has a sleeve instead of felt and o ring and shoud solve the false air.
The fitment of the carb is very nice and tight.

The engine response reasonaly well in the higher speed. In the low speed there is no response on the idle speed setting. I worked on the mixture but also there not much repsonse. Increased the pilot jet from 42 to 45 (main 72)

But my expectation would be that I 'always' would get some repsonse on the idle speed. Is that true ? Or can the mixture be so of that I can't control the idle speed?


Anu thought on this.

Try smaller idle jet.