What do I check?

Hi,
When I turn off the key, the engine sometimes runs on for a second or two.

What should I look at?

 

Sticking solenoid shut off valve on the carburettor

 

Check someone didn't fit a diesel engine while you weren't looking

 

Carbon on the pistons caused by over rich running. It runs as a glow plug engine using the glowing edges of the carbon to keep igniting the fuel. Its why the shutoff solenoid has to work...

 

^this