Take loose the nut that holds on the flywheel. Then hold the flywheel with a pair of pliers and lift it off of the workbench, make sure the flywheel nut is even with the top of the crankshaft. As not to damage the crankshaft of the threads. Then lightly strike the nut/crankshaft until the flywheel comes loose. It should only take a couple of taps.

You'll find Stihl Ts350 Fly wheel removal tools on eBay they are around £20. Easy enough to make if you have a lathe. Have a look to see what they look like and if you can make one up. It is a tube with an external thread 22mm ( I think), the tube is screwed into the flyweel and after nipping up, a bolt is screwed into a thread on the inside of the tube, this presses onto the crank and when tightened the flywheel is pushed off. The flywheel is a tapered fit on a tapered shaft and shocking it does release it. But personally I always felt like a gorilla particularly the first time when it has been stuck there for years and really refuses to release. Subsequently it is easy enough to release.