While you wait for answers, we may have found some information which could help you.
Click here for Tecumseh Engine SparkEngine runs wide open unless brake pedal is pulled completely back. Why?
adjust variable mechanism -- how/??
howcan i fix my rx73 riding mower?
How do I adjust the tension on a 42 inch yard machine belt ?
what to do to slow down the high rev?
Can't get front pulley off yard machine rider?