Too off the valve cover to replace the gasket on an L Head Briggs and Stratton 126T02-0301-B1. Only symptom I had was oil leaking from the cover (bad gasket) - engine ran fine. I noticed a lot of carbon build up in the valve case on the exhaust side. Was just going to clean up and move on, but was wondering if that is a sign of a problem to come or just normal wear and tear?. Any thoughts/help would be much appreciated.