I have a sears 17hp briggs&stratton which will not run a constant speed, it surgers up an down. What can I do to correct this problem?

Check air filter, adjust carb. clean carb. check fuel quality for contaminants.

Same problem with a 20HP. Believe it is the governor springs. If yoiu'vce cleaned the carb make sure the linkage is back the same way it came off: not upside down or hooked in the wrong way.

Hi,
It is not a bad governor spring! That is possible, but so unlikely as to boggle the mind. Just does not happen; dirty low speed circuit is the problem.
Peace,
Clarke