Hi Jack,....Unless you're running several engines simultaneously for long runs, I haven't noticed any unpleasant exhaust fumes...I don't run any fuel mixed lube & run the leanest mixer A/F ratio possible for quick starts & clean runs...I Do remember, when new & fiddling with various fuel lube mixes the exhaust smells..I lightly lube the cylinder wall before each run & enjoy closed vented home engine runs without shivers or fumes.....tom.