The decibel level of a stock Harley-Davidson exhaust can vary depending on the specific model and year. However, as a general guideline, stock Harley exhaust systems typically produce sound levels ranging from 80 to 90 decibels (dB) when measured at a distance of 50 feet (15 meters) away. It's important to note that this range is an approximation and can vary depending on factors such as the engine size, exhaust configuration, and any modifications or aftermarket additions that may have been made to the motorcycle. Additionally, local regulations and laws may impose specific noise limits that motorcycles must comply with.