Probably should not argue this topic again....
Whatever happened its fuel related he says he uses the fuel in his chain saw. Runs his trimmer empty every time. Perhaps this practice dried out some rubber parts in the carb. Or a small amount of fuel oil mix(a lot of 2cycle oil uses fuel stabilizer) maybe the oil dried and clogged something. In all cases the carb needs cleaned, rebuilt, or possibly replaced.
I would find out why it happened if something dried out keep fuel in it. Or whatever...
I'm not going to argue the topic, I don't have too. There have been to many articles wrote by different people and firms alike to prove what I said is correct. The shelf life of gasoline depends on the type of gas and the storage conditions and can range from a couple months to a couple years. One wild card is that gas you buy at the pump may already have been in storage for anywhere from days to months.
If the or his problem is fuel related it's easy to check all he has to do is try and start the engine, choke it, crank it half a dozen times and if it doesn't start pull the plug and see if it's soaked with gas. If the plug is wet he is getting gas and it's not a fuel related problem unless his mixture is wrong.
Check all your electrical connections, change the gas filter, change the two air filters and clean the spark arresting screen and a new plug first before you start tearing into the carb. Simple things first.
I've been on this forum basically since it started and I seen a lot of threads about people having problems with Trimmers, Edgers and alike and it seems that the greatest majority of the problems ( not All) with this equipment not working have something in common and that's the use of fuel stabilizers, seems like to me the people who use that stuff are the ones always having problems???