Spray penetrating oil around the interface between the crankshaft and the timing gear. Then make a tool using a flat plate with 2 holes aligned with the 2 x M4 threaded holes in the timing gear. You can lever the plate and it should allow the timing gear to come free. Alternately drill and tap a hole in the centre of the plate to insert a bolt that will push against the crankshaft whilst the 2 x M4 bolts will pull on the timing gear. There is possibly a genuine tool for this but I haven't come across it yet. Be careful with the M4 bolts as they seem a bit flimsy in this application.