to keep dirt out and oil in
The tappet cover(s) is located on the cylinder head, it is usually round in shape on a motorcycle. On a car, it is more commonly known as a "valve cover" and is the rectangular shaped cover & all the four corners has chamfered shape
If your tappet cover is perished, you will clearly see leaking oil coming from the join of the head to the block. If you clean the area thoroughly, you will notice with a day or so of normal running if you have a leak.
there are no ignition coils per say, there is an injector loom under the tappet cover that has connectors going to the injectors. to change that remove the plastic engine cover (3 bolts, 2 on left side 1 on the right). remove the hose from the top of the tappet cover it has a spring clamp. remove 8mm bolts on tappet cover, remove tappet cover and the injector loom is the long plastic harness on the right side. you will have to replace the gasket and seal the half moon at the rear with high temp silicone. sorry i was thinking TD5 engine. there are 4 bolts 8mm bolts attaching the coil to the rear of the engine, they are difficult to access. remove the leads from coil pack, you will have to remove the plenum chamber as well to manouver the coil out.
The tappet plate in an AEG moves the air nozzle back and forth to feed BBs into the hop-up chamber for firing. It is synchronized with the gearbox cycle to ensure proper feeding and firing of BBs.
That would be a hydraulic roller tappet valve train.
WHAT ARE THE TAPPET SETTINGS FOR A PEUGEOT 306
That would be the flat tappet cam in that engine.
its a breather hose which helps to reculate sump preasure should replace it
single, an easy way to tell on most cars is to pull off the tappet cover and count how many cams there are :D
200 ford ranger tappet valve clearance
in case it explodes. the cover protects you from the acid inside.