 |
Venting the Fuel Tank This repair procedure was provided by Doogie, VROC #12748. "As fuel is being pulled from the tank, a vacuum is created due to the fuel vent not letting in enough air, so eventually the vacuum becomes enough to where it overcomes the vacuum in the petcock."
Actually, fuel is not "pulled" from the tank; it is gravity-fed to the carburetor float bowl. Also, there is no "vacuum" in the petcock; the petcock has an internal valve in the On and Res positions that is controlled by vacuum from the carb. IOW, no fuel flows in these positions unless the engine is running. Engineers... "A good way to test this is to put an extra key in the gas tank lock, and if your bike starts to quit, pop the gas tank open. If the engine comes back to life, you know you have a vacuum problem in the gas tank." Just a note here; this is not recommended while you're still riding down the road! Try to find a safe place to pull over and stop before popping that cap... RW "Here is how I got rid of the problem: "1. Ensure that your air plenum (the plastic behind the air filter) is on tight. The bolts on mine had vibrated loose, which allowed the plenum to move, which in turn causes problems in the main vacuum hose coming off of the plenum." For the rest of us, he's referring to the air cleaner backplate and the carb boot. There is no "vacuum hose" attached to the backplate. RW "2. Remove the gas tank cap by removing two screws behind the hinge. "3. Disassemble and clean the parts of the gas tank cap as sometimes dust can partially plug the labyrinthe (passageways). Be careful, it's not hard to disassemble, but some of the parts are small and can roll away from you. "4. While the cap is disassembled, take a look at the bottom of the cap. You will see a small hole. This is the fuel tank vent. If you take a closer look, you can see how the spring from the locks protruding out the sides partially blocks the hole. My theory is that the spring blocks the hole enough that air can't flow through fast enough to prevent a vacuum. Take a drill bit and open up the hole. I also drilled two extra holes (one on each side of the center hole) to help with ventilation." Not having done this mod, I've no recommendation for bit size; but don't go too much bigger! RW "5. Put the gas cap back together and re-install on the tank. "6. While you are at it, take a look at the vent hole coming up through the gas tank. You can identify it by matching it up to a teat on the gas cap at approximately the 5:00 position when looking down on the tank. Take a air hose and air gun, and blow low pressure air through the hole in the tank. You should hear a hissing noise, which is telling you the vent line is open. If you don't look for a bend or kink in the rubber vent line running underneath the bottom of the tank on the RH side." Note: On later model 800s, there are 2 vent lines on the right side of the fuel tank. These lines can be cut a few inches from the nipples and attached together with a T-fitting. One line to the back of the bike can then be eliminated. RW "I did this repair and haven't had any problems since then."
 
All rights reserved
|
RW
