Briggs & Stratton 3.5 HP A736008 MIN [SAE J607] Mower starts right up - runs fine for a minute then starts to miss and run rough - runs fine again for awhile just before it goes MT. Any suggestions to save me time trouble shooting appreciated.
How about getting us the model type and code off of the engine, so we can see what you are working on.
The older briggs engines will have it stamped into the metal housing above the spark plug.
The 3.5 and other numbers is the rated HP with the standard that was used to test it. Sometimes the model number info will be stamped above the muffler.
I would start by replacing the diaphragm between the carb and tank. Could be related to the fuel pump part of the diaphragm or the auto choke part. If you haven't replaced the plug yet, that would be a suggestion also.