FUEL SYSTEM

CARBURETORS, AIR CLEANER & GAS TANK

HOW IVAN GETS GASSED UP WITHOUT VODKA

FUEL TANK

   The fuel tank on a Dnepr has two main purposes.  First is to retain the fuel that is to be delivered to your carburetors via a petcock and two rubber hoses, and second is to leak fuel all over your motor and leg at the worst possible moment.  If you have the opportunity to do so, I suggest that you coat the inside of your gas tank with an appropriate liner such as Kreem.  There is a kit called the Kreem Combo Kit which consists of a concentrated cleaner and final rinse that remove loose rust and dirt inside the tank and condition the inside surface for tank sealer.  (Tank prep A and tank prep B) There is also a third component the Fuel Lank Liner which when cured provides a tank within a tank.  You must remove the petcock as this stuff will also seal up the screen in the petcock.  It is available at most Harley shops, or online at www.deniskirk.com.   Follow the instructions, and let it cure up properly before refilling with fuel. 

   If you should spring a leak in your gas tank, it is generally found at the petcock.  Most of the time it can be repaired by simply removing the petcock, and putting a little plumbers Teflon tape on the threads and screwing it back in.  The tape can be bought at any hardware store generally for less than a dollar.  If the leak is not in the threads, you can seal it up with a little braze, but this is dangerous, and should be done by a professional.  Before you take the tank to him, it should be drained, thoroughly rinsed and dried and aired out for a few days.  I have personally gone so far as to spark a BBQ lighter inside the tank after rinsing to clear it of residual fumes but this is both dangerous and stupid and absolutely not recommended.  If your face is near the filler hole you can get burned, and if there are excessive fumes the explosion can rupture the tank beyond repair.  Sometimes a pin leak can be repaired with an epoxy such as JB Weld or one of those two part epoxy fillers for a temporary fix.  In an emergency, a small leak can be repaired by simply rubbing it with a bar of old fashioned soap, either hand or laundry style.  Not one of those fancy soft, pure perfumed bars but a cheap bar of hand soap or lye soap.  I personally carried around a bar of soap in my pocket for a whole summer and kept a leaky tank semi sealed up until the season was ended.

   Inspect your fuel tank for cracks and dents when you have it off, and while you are at it, pix the chips in the paint.  To find a mystery leak, with the petcock shut off immerse the tank in a tub of water and pump in some pressurized air.  Do not exceed 0.04 MPa (0.4kgf/cm2) of air pressure.  Wherever the little bubbles are coming from is where yo7ur leak is.  Wash the tank inside with a 10% solution of soda and water to remove rust and dirt. 

REMOVING THE GAS TANK

   Before you remove the gas tank, it is best to drain it.  Disconnect the fuel lines from the carburetors, and drain the fuel into a pair of approved gas containers.  Do not drain them into open pans or glass jars.  Up under the gas tank at the front is a rubber hose that connects the two sides of the tank.  This is a fuel equalizer and its purpose is to keep both sides of the tank with equal amounts of fuel when the tank is low.  There are generally a couple of hose clamps holding this in place, but not always.  If there aren’t any clamps, then get some. 

   Undo the bolt that holds the front of your gas tank to the backbone of the frame, and the two bolts on the underside at the rear of the tank that hold it to the tab on the frame.  There should be a rubber washer under each of the bolts, but that is not always the case.  It’s not a bad idea to either find an appropriate rubber washer, or make a vibration guard out of a piece of rubber or cork gasket material.  Slide the tank forward and lift the rear of the tank up to clear the frame, then slide it backwards and lift the front free.  If you have a bench seat, this must be removed to be able to get the gas tank off.  Put it back on in the reverse order.

FUEL COCK

   Remove and inspect your fuel cock (petcock) for excessive rust and dirt particles.  Be sure that the cock allows adequate fuel to flow equally from both spigots.  Remove the settler bowl at the bottom of the petcock, and clean the filter with solvent or gasoline.  When you put the settler back on be sure not to over tighten it, as it is aluminum and strips quite easily.  Replace all of the rubber hoses with new fuel line.  It’s only a few dollars, and can save you a ton of headaches in the future.  This is absolutely necessary if the lines are cracked or swollen.  New fuel lines and clamps is one of the cheapest fire insurance policies you can get for your motorcycle.  A little spray of soapy water can make the installation of fuel lines a lot easier.  Be sure to tighten all of your hose clamps properly when you put it all back together.

   On the bottom of your gas tank at the R.H. rear there is a threaded bushing where the fuel cock screws in.  It is advisable to use a little Teflon tape on the petcock when you install it to reduce the chances of seepage.  One or two wraps is more than sufficient.

   At the bottom of the petcock is a sediment bowl, (settler) which contains “a filter gauze”, (a wire mesh screen of copper or brass) and a rubber gasket.  The gasket can be replaced with a rubber O-ring if it is damaged.

   The main body has two fuel line pipes.  The main fuel line pipe sticks up about 1¼ inch, and the reserve fuel pipe only sticks up a few mm.  The main pipe is located in the center of the reserve pipe. 

   The on/off/reserve valve is also found in the main cock body.  It has one axial and two radial holes.  One of the radial holes is coincident with the main fuel pipe, while the other is coincident with the reserve pipe.  On the other side of the main body is a dual spigot, each of which is connected to a carburetor via a fuel line.  The cock valve has 3 positions, (see diagram).  O (all the way to the right ) is fuel on, P (center position) is off, and 3 (all the way to the left) is reserve.  The reserve contains approximately 2.1 liters of fuel.

   Finally here are a couple of thoughts.  Unless you’re a purist doing a restoration job, I suggest you add in a couple of in line fuel filters.  You can get them anywhere that sells motorcycle parts, and there is a full gamut of pricing.  Most folks prefer the ones with the clear cylinder which makes it easier to monitor the fuel flow.  Mr. Gasket makes a nifty chrome unit with a replaceable element that is compatible with all fuel lines, 1/4” 5/16” and 3/8”. Go to www.mrgasket.com for more information on this little gem.

   Red Line Oil has another useful product on the market.  It’s the SI-1 Complete Fuel System Cleaner.  Its concentrated, high-temperature detergents clean fuel injectors, carburetors, intake valves and combustion chambers.  One bottle treats up to 100 gallons.  For more information, you can go to www.redlineoil.com.