I refurbish them for resale.
The first thing I do when I get a non runner (most of them), is to drain the fuel and strip the carb. Nine times out of ten the reason they don't work is when people lay them up over Winter without draining the petrol. The petrol goes off and the carb generally is gummed up and corroded.
A couple of years ago I purchased one which had been run from new on Aspen 4 Alkalyte lawnmower petrol. The mower was over 15 years old.
I stripped the carb and it was spotless inside and out, almost like new, with no corrosion. The jet wasn't blocked and even the O rings were soft and malleable.
Since them I have run my lawnmowers and strimmer on this. I never have had a problem with non starting after over a year between seasons, even though I never drain them.
It has a shelf life of 5 years,as it is ethanol and benzene free.
There are other brands, Viking for example.
I know it's about £20 for 5 litres and it'd be far too expensive to run on it, but it'd save hassle of having to strip a laid up motorcycle after the Winter. Just add a drop and run it before you hibernate. Modern petrol goes off so quickly.
Just a thought.
