EXTRACT from: https://www.pbo.co.uk/expert-advice/how-to-service-a-2-stroke-outboard-engine-24833
Parts one (1st week)
1: Drain the old fuel
The most common complaint might be : it worked fine last year but now it won’t start. This is because petrol evaporates over time, leaving behind an oily, paraffin-type residue which gums up the carburettor. So the first step is to drain the old fuel.
1: Remove the fuel pipe from the carburettor by loosening the clip with a pair of long-nosed pliers.
2: Turn on the fuel tap and drain it into a container.
3: If necessary, remove the tank and clean out any residue or gunge. There is often a small filter just above the fuel tap.