I am looking for a pattern to the Toro ProLine Suzuki knocking problems that has been frequently reported on this site. If you have a Toro ProLine with a Suzuki mower, whether you have the knocking problem or not, I would appreciate a quick reply to the following questions. I will gather this information and report back my findings to this thread. If you do not know for certain the answers, feel free to give me an educated guess, BUT LET ME KNOW IT'S A GUESS. Also, if you have multiple mowers, please answer multiple times (once for each mower). Do you have the knocking (a.k.a. rattling) problem (Y or N)? What metropolitan area are you near (I'll check for EPA requiring special fuel additives)? What year was your mower manufatured? What model is your mower (BBC, zone start)? How many estimated hours wear before the problem began? How many estimated hours per week do you run on your mower? What horsepower rating is your engine? What type of oil and what ratio to you use? What type of gas and what octane do you use? What make and part number is your spark plug (this may be important!)? Does your engine run lean or rich (based on plug inspection)? Any other notes or comments? Your time will not be wasted. Feel free to elaboate. I hope to solve this annoying problem.