It is possible it is the carbs. Since he only has 1 set, it best to start at the beginning. Timing advance can cause this issue and is easy to check.
PLugs will tell him if he is running too rich or too lean. And can then tell him exactly where to look on his carbs to fix.
Besides, pulling the carbs right away is a pain in the ass, especially if it turns out to be something else.
The ride IS the adventure. The destination is just to get gas!