The first thing to do is remove the fuel cap assembly. Open cap and remove the 4 phillips screws in the cap base. These phillips heads can strip out easily, so make sure you have a non-worn, good fitting screwdriver. Put all your weight pushing the screw driver down into the screw while turning until it is broken loose. Remove the cap assembly. It’s a good idea to cover the tank with 2 layers of towels with a hole in the middle to access the inside of the tank. This should prevent paint damage from dripped fuel.
Note that there is an open slot in the cap base between the two left screws. This aligns with the hole in the tank between the two left screws. This is the cap rain drain that keeps rain water that collects around the cap from entering the tank. There is a tube inside the tank that drains the water out the bottom. When reinstalling the cap, the hinge MUST be towards the rear of the bike to allow the drain to work properly.
The tank is aluminum, so the inside of the tank SHOULD be bright shiney silver. If there appears to be a light brownish bathtub ring on the lower part of the tank, that is the first indication of the pump damper breaking down.
The next thing to do is drain the tank. The tank will NOT gravity drain by merely removing the hoses from the tank due to the routing of the tubing inside the tank. Yes, a little fuel will come out, but not the majority. The best way to drain the tank is with a transfer pump. A very good inexpensive one can be bought from Harbor Freight or Summit Racing. I have a couple of the Harbor Freight ones that I’ve used for years with great results.
Battery-Operated Liquid Transfer Pump
Amazing deals on this Transfer Pump Battery Operated at Harbor Freight. Quality tools & low prices.
www.harborfreight.com
https://www.summitracing.com/parts/wmr-w54172#overview
After draining the tank, again look for discoloration below the fuel level.
Next, you will want to remove the fuel pump. It is mounted to a shelf inside the left front of the tank. Part #4 in Rob’s image above has a clip on the front and rear of it that holds the pump down to the shelf. It releases by pressing both tabs towards the pump.
There were two different fuel pumps that came on the Flying Bricks. The 52mm pump was used on bikes built before 1/93 and the 43mm pump that was used on bikes built after 1/93.
The pump on the left is the 52mm pump with the very delicate “cup” inlet screen. The pump on the right is the 43mm pump with the more robust “sock” inlet screen.
If you want to know which pump you have before removing it, look for these wrinkles in the housing at the top of the pump. If it has the wrinkles, it is the 52mm pump with the delicate screen. Be VERY careful while lifting this pump out of the shelf so as not to tear the screen on the cup. If it doesn’t have the wrinkles, then you have the 43mm pump (or perhaps a 37mm aftermarket pump) with the more robust sock filter. The only issue with that is it requires a little more manipulation to get the sock through the hole in the shelf, but it shouldn’t tear.
BEFORE removing the pump, have a 6mm and 7mm wrench (or a tiny crescent wrench) on hand to remove the wires once the pump is out of the tank (the wires are long enough).
Take a long screwdriver or a 7mm nut driver and remove the hose clamp from the short hose that is connected to the fuel filter. Disconnect it from the end furthest from the filter and leave the clamp on the tube in the tank. Disconnect the hose from the tube. Drain as much fuel as you can from filter into tank.
Now, lift filter and the attached hoses straight up out of the tank until the hose is tight. Now reach into the tank with the other hand and grip the two tabs in front of and behind the pump. Squeeze them together, toward the pump to release them from the shelf.
Use the hand on the filter to provide the lifting and the hand in the tank to guide the pump through and clear of the shelf. Once clear of the shelf, remove the hand from the tank and lift pump out of tank. Disconnect wires once pump is outside the tank. Small terminal is positive and large terminal is ground. You do have the key off, right?
Take pump to bench and test with a battery. Just briefly touch wires to appropriate terminals. If it doesn’t turn over, try briefly reversing polarity to see if it will unstick. If it can’t be unstuck, you need a new pump.
Check the rubber vibration damper surrounding the pump for deterioration. It should have the consistency of a tire with no gooeyness and no transfer to your finger. There should be no missing areas around the lower edge.
Now you get to thoroughly inspect the tank. First, with a flashlight and small inspection mirror, inspect the well below where the pump mounts. That is where any dissolved pump vibration damper will settle first. Is it clean enough to eat out of? It better be, because that’s what you pump, filter, injectors, and motor will be eating if it’s not!
ALL hoses used in the fuel system MUST be rated for fuel injection (100 psi+)!!!(Except the vent hose used on the 54mm inlet screen)
ALL hoses used inside the fuel tank MUST be submersible rated!!!
Let us know what you find and we’ll go from there. Who knows, you may get lucky, if no one has pumped any crud through you fuel system. WAY better to check first than just roll the dice.
