It probably is due to the crud that is around the filter in the bottom of the tank. Petrol is messy stuff and as it is a hydrocarbon it contains water. Water rusts the tank this sinks to the bottom and after a while gunges up the filter. If possible empty the tank fill with a small amount of fresh petrol and swill it around and empty again. If you can remove the filter from the tank clean it in meths or clean petrol. An old toothbrush works well.
Answers & Comments
It probably is due to the crud that is around the filter in the bottom of the tank.
Petrol is messy stuff and as it is a hydrocarbon it contains water.
Water rusts the tank this sinks to the bottom and after a while gunges up the filter.
If possible empty the tank fill with a small amount of fresh petrol and swill it around and empty again. If you can remove the filter from the tank clean it in meths or clean petrol. An old toothbrush works well.