The correct spark plug gap for the stihl 038 chainsaw is 0.020″
Good to see the old Stihl saws still out there, they were made in the early 80’s.
There is a parts list and service manual from this website, just use the search at top of page or go into the manuals section for viewing online or download it.
Just for the record here is some other interesting specifications for the Stihl 038 chainsaw:
The basic 038 model’s single-cylinder, two-stroke engine was rated at 3.3 kilowatts, or 4.43 U.S. horsepower, from its 4.07-cubic-inch displacement. It had a 1.97-inch bore and 1.34-inch stroke. The slightly more powerful single-cylinder Stihl 038 Magnum was rated at 3.6 kilowatts, or 4.8 U.S. horsepower, from a 4.4-cubic-inch displacement with a 2.04-inch bore and 1.34-inch stroke. Both models weighed 14.6 pounds without bar and chain.
Good luck with your servicing work!