Before checking the output of the pump, first remove the rubber plug from the right side of the pump, just behind the exhaust. That will expose the throttle cable controlled portion of the pump. You'll want to adjust the cable so that the cable will move almost immediately upon twisting the throttle.
Once that is done, remove the seat & gas tank. Then remove the small hose running from the pump to the carburetor. Drain the carb, then mix up some premix in a remote container & hook up to carb. Fire up the bike & watch the end of the hose that you disconnected -- oil should come out every couple seconds at idle, & faster with RPM.
If you don't see any oil coming out, remove the black plastic cover for the pump. you will see a small screw that has both a phillips head & a hex head for a 8mm socket. It can also be identified by a sealing washer. Remove this bolt completely & oil should start to come out the hole. When the oil flows smooth & without bubbles, re-install the screw, & cover, then fire the bike back up on the premix & watch the hose again. If there was any air in the line, the oil should flow within 30 seconds at idle.
Drain carb again, hook hose back on to the right side of carburetor, re-install seat & tank & hook tank line back up, & turn gas on. You should be good to go!
If you have any more questions about this bike, feel free to ask away. I currently own 9 of these!
This was my first bike back in December of 1985.
Yamaha BW80 Oil Pump? 
Linear Mode
