I know at least for the front cover of the timing advance, you need a funky torx-type tool to fit into the bolt heads. Not sure if you need those for the rear cover where the timing advance lever is or not. But anyway if it's got the torx, don't use an Allen as the bolts can be corroded in and it takes a lot of force required to break them loose, which will run a high risk of stripping those torx bolts.