Modern Vespa

I've been trouble shooting this bike for my very occasional rides.
It's very difficult to start when cold and almost impossible to ride until it warms up and even then it lags.
I've replaced the plug,cleaned the carb a number of times with carb cleaning tools and air.
Checked for air leaks and no signs of cracking on any hoses.
I did read with interest that tight valves may cause this issue so I pulled the valve cover off and was not happy to see this big is a shim only adjustment
I could not get a 006 feeler gauge in on intake or exhaust.
Can anyone send me a link or info on how to get more clearance
Do I really need to drop the engine and remove the cam?
Thanks for the help

I looked at the parts fiche for an LX50 with a 2V head, and that has screw and locknut valve lash adjusters mounted at the ends of the rocker arms.

I don't think that Vespa has used a shim-under-bucket arrangement in any scooter (but I am not a long-term Vespa-ist).

I better run the serial number
I did pull the cover and no adjustment but
I wonder if it's an lx
The valve cover has an odd name on it so I'll get more info in the morning
Thanks