Small Engines (Lawn Mowers, etc.): 17hp Briggs OHV Rough Running, walbro carburetor, briggs stratton

Question
This is as much a commentary as a question. I have a 17hp OHV AVS I/C Briggs & Stratton vertical shaft engine, with pretty much the same experience as some others i've read. Multiple trips to 3 different repair shops due to rough running/backfiring. I would get it back and it would run ok for about half of my yard (.45 acres). Finally I just started checking all systems from fuel to electrical, found the exhaust rocker was loose, looked up the specs and adjusted. Ran fine for most of the rest then started again, loose valve the culprit again, replaced rocker set screw still the same results. No damage to rod or valve. Removed the head and pushed against both tappets with a rod while turning the crank, perfect movement on lower (intake) tappet but no movement on upper tappet. I'm guessing there is damage to the cam or tappet inside of the block. My next step is to remove the engine and open it up to look for damage. While i'm not a mechanic I have a fair amount of common sense . Is this the proper step in your opinion?  model#31c707 type:0154e1 code:030421ze   Thanks for listening

Answer
Do you have the Nikki or Walbro carburetor?

You could take the engine apart but I'm not sure if that is the best solution.  I have not seen any specs for the cam lobes but a keen eye may detect some wear.  If you take the engine apart you will need to replace the base/sump gasket and the lower oil seal.

All Briggs engines have a mechanical compression release with most being on the exhaust lobe of the cam; this is most likely what you are seeing.

Have you removed the valves and inspected the seats and valve faces?

Let me know.
Eric