The condition of the stick coil’s plugs is not a good indicator of stick coil operation. The lower plugs keep firing and keep the combustion chamber and center plugs clean(ish). The coil/rpm drop is necessary to determine coil condition. If the mfg. date is before ‘09 be ready to replace a currently serviceable coil soon. Checking its operation is easy: see photos.
Fuel tank removal is hard: see more photos.
A clogging fuel filter or leaking internal hoses will cause stuttering on acceleration and going uphill. To replace the fuel filter (and hoses) the tank must be removed. Left and right body work must come off. There are 14 machine screws attaching the L & R fairing to the frame. There are two fasteners that get overlooked (and therefore broken off) when removing the the L & R bodywork. They are directly behind the BMW emblems. They can be accessed from top or bottom. When lifting the fairing panels be ready to disconnect the turn signal connectors. Don’t forget to reconnect them on assembly.
The tank is aluminum and can be shorted to the positive battery terminal. Make sure the positive terminal is covered or the ground wire is disconnected. Two forward bird’s mouths rest on frame-mounted rubber biscuits. When the two hold down machine screws are removed, a 2 X 4 X 4 block can be inserted between the top of the battery and the pivoted-up tank. This will make the next few steps easier.
This era S may have plastic fuel disconnects on the right side, just above the right throttle body and hidden by the fairing. They are very brittle and will break. Don’t move them until you have a catch-pan ready for the fuel leak. They may have been upgraded to aftermarket steel, if so no breaking problem and no need for pan or pinching. There is a hard black plastic fuel pressure and divider manifold upstream of the TBs. The flexible fuel lines are connected to this manifold. DON’T pinch the plastic manifold-tubes!
The fuel pump power and low level light sender-wire connector is on right, inside, under the tank. Two machine screws attach the tank to the frame. One machine screw secures the air snorkel on the left side. This mates with a female receiver that is a threaded hole in the frame. Be careful on assembly not to strip it.
Once removed, drain the tank and lay it on its right side. Index all the flexible lines to their attach points. Colored zip ties work well and can be permanent indicators for the next disassembly. One hose will need to be disconnected in the tank to pull the assembly out of the tank.
The fuel pump assembly plate-to-tank, large o-ring seal is reusable. Factory swaged hose clamps are used throughout the plumbing system. Be careful when mechanically-expanding them. Prying from one side only can fracture brazes on the fuel pump plate assembly. Applying leverage with small awls on both sides, at the same time will uniformly expand the clamps. Replace with screw-type hose clamps. The hoses should always be replaced with new hoses regardless their condition because you don’t want to do this again anytime soon.
Check the stick coils first.
