Modern Vespa

hi,
I am using Vespa P 150 x. Almost a year ago my vespa plug was showing rich. A mechanic adjust carburetor and then my spark plug was showing
lean. The check my spark plug every month it was lean but now this month i check the spark plug it was showing Rich.

The pick of my scooter is v good. One the smooth road i can drive it upto 80 Km "the speedometer meter show"

The question is, is there need to adjust the carburetor for more batter pick ? so that my spark plug may show lean ? I know that the air and fuel mixture effect the result on the spark plug for lean and rich. Iam attaching the picture of the plug condition and my fall in Number 5 i.e "Too Cold". I am using spark plug of " NGK BP6HS"

To adjust the carburetor for lean kindly guide me that should it move the air fuel mixture screw clock wise or anti clock wise ? In clock wise more air will pass or vice versa ? what is the technique ?

Thanks in advance.

That carb in the picture is a 20/15. It should be a 20/20 on a p150. You might have more problems then just your mixture screw

Well this carb is working smoothly on my vespa since last 10 5 years.My fuel average is also very good . My scooter is working smooth. Technically what is the difference in between 20/15 and 20/20.

Well if i change it to 20/20 then how may i adjust the mixture screw it for lean plug ?

If it's working then fine. It's just not normal for that model.

To make it richer turn the mixture screw counter-clockwise.

Wait a minute. I don't think I understood you right. If your plug is black and you want to make it leaner screw it in clockwise.

Thanks "Warhorse" for your kind reply. Well guide me that how much turn should I give it ?

It's not that easy or simple.

If it's still running fine and plug is just a bit blacker than normal, don't worry about it. Just ride.

Read this until you understand it
http://vespamaintenance.com/fuel/carbtune/

Greate....