I have been using my 1999 rear engine 11.5 hp B&S, for about 7 years. Last week it sounded like something had come loose inside so I killed the engine. Oil was good, gas was fine, no obstructions on blade. I decided to try to start it back up, so gave a pull and she started right back up, sounded good. Only problem is that now the throttle does not regulate the motor speed. It works the choke just fine, but the engine only runs at one speed. I can't find anything out of place as far as springs and linkages. Everything seems to be moving correctly according to possition of throttle lever. Can anyone give me any ideas about what may have made the clattering sound and why the carb doesn't seem to care when the throttle position is moved?