Spent the weekend doing maintenence on my '91 B4.
CDI : I replaced the 4 main caps about a year ago and the bike has been running great since then. I went ahead and replaced the 5th cap (marked C4 on the board) just to make sure it doesn't fail at a bad time.
Carbs : Drained the tank and put in fresh gas. Also found my fuel line was slightly pinched between the breather cover and tank. Disassembled my carbs and managed to strip the head on one float bowl screw so I relpaced all of them w/ socket head cap screws. I'm glad I had a screw extractor. Sprayed the carbs down w/ carb cleaner and brushed the insides and ran a thin wire through all the jets. Blew everything out w/ my air compressor. Checked the 0-rings, needles, and floats and put eveything back together.
Coils and plugs : Removed the spark plugs and brushed them clean. Disassembled the wires and plug caps from the coil packs and reassembled them making sure the connections were tight. Checked resistance on primary and secondary coil windings.
Coolant : drained and refilled coolant w/ 50/50 Prestone and distilled water.
Valve adjustment : Removed coolant hoses and cylinder head cover. The manual says to remove the radiator, too, but I can get the valve cover off w/ the radiator in place. Removed all the gasket sealant from the valve cover gasket and checked the condition of the gasket. Rotated the cams to the correct timing positions and adjusted the intake valves w/ a .005" feeler guage and the exhaust valves w/ a .007" feeler guage. BTW, the square head valve adjustment screw is the same size as an SQ2 square socket driver (kinda hard to find, tho). Re-torqued the cylinder head nuts according to the manual, but couldn't get to nuts 3&4 (labeled in the service manual) because they were obstructed by a tube so I left those 2 alone. Used new gasket sealer on the gasket and replaced the valve cover. Used a little gasket sealer on the valve cover bolt gaskets and torqued the bolts down according to the manual.
Put everything back together and after a minute of cranking to fill the float bowls, she beltched some black smoke and started up. Let her warm up w/ a little choke then turned off the choke and adjusted the idle speed screw to a little over 1K RPM.
Then I took a well deserved ride in the beautiful 70deg Dallas weather.