I have a McCulloch Titanium 46SD mower. The engine seriously "hunts" when going. I took out the spark plug and noticed it was completely black. I cleaned it but it has no effect, the engine still hunts. I think at the end of last year the mower was filled with a 2 stroke oil / petrol mix in error instead of standard unleaded petrol.As there is a very long waiting list at this time of the year for repairs, can anyone suggest if I could fix this.
Many thanks for any replies

Frank, May 2008

The hunting is caused by an over-rich mixture.

If this is a briggs engine with the carb on the tank, it needs a new diaphragm.

If the engine is equipped with a choke control, check that it is not sticking in the 'on' position. Tecumseh engines arw prone to this.

Phil Saunders, May 2008