It's a toxic job but sometimes you have to do it.
Removing the fuel tank on a dirt bike gives you access to sections of the bike for repairs and other maintenance needs. But you need to drain it first. Preferably, somewhere outside and not in the confines of your garage.
Four out of five riders agree: Riding till the gas runs dry offers the best way to empty a fuel tank. But unfortunately this option doesn't always coincide with the need to remove the fuel tank. Therefore drain the remaining gas by removing the fuel line and let it pour into a receptacle. If you want to reuse the fuel, drain into a clean container like an existing gas can, otherwise don't reuse the gas, at least not in your dirt bike.
Look for a black rubber tube from the gas tank that feeds into the motor. Remove the clip and work the tube free. Use pinch pliers on the tube an inch or so in from the connection so gas doesn't spill before you can position the tube over the catch basin. Once free, release the pinch and let the gas flow into wherever you plan to catch it. It helps to open the gas cap to allow easy flow of the fuel. Now you have an empty tank and you can remove it.
As for bikes with a petcock follow the same path as described above but instead of removing the fuel line from the engine remove the fuel line from the carburetor. Keep the petcock in the "off" position (no need for pinch pliers) until you free the tube then turn it "on" to drain the gas. You can also leave the petcock in the "off" position and remove the gas tank filled with gas. In fact, draining the gas is optional unless you plan on working on or in the gas tank. Draining the gas, of course, makes it lighter and easier to remove.
Mechanic's Note: If your bike uses a "remote" petcock meaning it is not attached to the gas tank then you would remove the fuel line at the petcock and use the pinch pliers to prevent fuel from spilling.
Strap from subframe to fuel tank needs removing
Some dirt bikes have a fuel tank strap on the subframe. Remove the seat for access to the strap. (You have to remove the seat anyway to access the gas tank.) Remove the strap then unscrew the radiator shroud bolts tightened to the radiator (two or four depending on model) and the bolt by the steering head (you don't have to remove the bolts tightened into the gas tank). The gas tank should now easily remove from the bike with the shrouds attached if you left in place the bolts tightened into the tank.
Reasons for Removing the Fuel Tank
So why would you ever remove the fuel tank? Lots of reasons including the following:
- Replace, repair or clean gas tank
- Drain old gas (then clean)
- Replace or repair petcock/petcock filter
- Repair or replace fuel pump/fuel filter
- Top end replacement
- Change spark plug (4-strokes)
- Check or adjust valves (4-strokes)
Riders who crossover from Moto to trail riding or other long distance riding prefer a large gas tank for the long haul therefore remove the smaller tank in favor of the larger capacity version. Metal tanks that rust, need dents removed or painted (mostly applies to vintage dirt bikes and street bikes) also requires tank removal and of course so does replacing a worn out tank. And, the very nature of riding in and around dirt while adding fuel either at the track or on the trails eventually gives way to dirt getting inside requiring cleaning.
Oversized fuel tanks sometimes come stock or can be installed aftermarket for longer trips
Elsewhere, most fuel pumps sit inside the gas tank explaining the need to remove and drain the tank prior to working on the fuel pump. Some 4-strokes bikes require tank removal for spark plug changes and valve checks or adjustments.
Any work on the petcock whether replacing, fixing, or, if applicable, changing the filter also requires draining and removing the fuel tank. No need to drain the tank when working on the top end or deep cleaning the bike around the engine block just make sure to use the pinch pliers or turn the petcock "off" and place the tank away from your work area to prevent possible contamination.
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