My bro-in-law had one. When mileage started dropping, we found the cat was plugged up. We replaced the cat with a section of pipe and all was good. Next time I see him, I'll ask if he remembers the numbers. If inspection is mandatory in your area, some guys used to ram a bar through the cat to clean it out...permanently. That would keep cat inspectors happy. Good reliable motors if they aren't over worked.