After refueling my trimmer, it won't start. I may not have the right ratio of oil to gasoline. Is there a specific way to purge the fuel system and start again with the correct gas oil mix?

If you haven't used it for awhile,the gas might also be old. Drain it out,and using regular gas,add some 40/1 fuel mix. The bottle or can it comes in will tell you the ratio for your particular tool. Also clean and oil it while you are at it.