Hi Okidoke.
You may have to take the carby off, remove the throttle butterfly in carby throat and remove the rod and clean it up.
Whilst you have it off, I would advise just doing cleaning the carby out at the same time, with new bowl gasket, etc. That way it will remain a reliable mower
Sometimes they have a little felt pad on the top to prevent dust ingress. Remove this with the shaft and soak in petrol to get the dirt out
