March 5, 2012

The Cure for the Classic Harley Leaky Fuel Valve

The fuel valve on my 1964 Harley-Davidson Duo-Glide, tends to leak a little now and then.  It’s not a major problem, but I decided it would be a good idea to fix it before it dumps a couple gallons of fuel on my garage floor.  The original valve uses a metal tipped rod that is tightened down against the lower tank fitting to shut off the fuel.  This tip has to be carefully lapped so it seals perfectly with the brass insert inside the lower tank fitting.  Use and age slowly wear out the tip and brass insert until fuel can start seeping past the valve, even when it is tightened down.

If your not interested in learning the fine art of fuel valve lapping, then I suggest you do what I did and call up Carl’s Cycle Supply.  They have just released a new fuel valve that uses a tip made from Peek.  For those chemistry buffs, Peek, which is short for polyether ether ketone, is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures.  The bottomline is that this tip will seal better and last longer than the original without the need for periodic lapping.

New Fuel Valve

New fuel valve from Carl's Cycle Supply

The first step to installing the new fuel valve is to drain the fuel tanks.  An easy way to do this, if you don’t have a siphon, is to detach the fuel line down at the carburetor and add a length of rubber tubing to the end of the metal fuel line.  Then you simply route the rubber tubing to a gas can and open the fuel valve.  Make sure you pull the knob all the way up so that it is on reserve.  Once the fuel is drained, remove the crossover line where it connects to the right side tank.  At this point I went ahead and removed the tanks, but that is an optional step.  If you do plan to remove the tanks, it’s a good idea to loosen the lower tank fitting while the tank is attached, so you can get decent leverage on the fitting.

Lower Tank Fitting

You'll need a 1" wrench to remove the lower tank fitting

Now you can disassemble your old fuel valve.  Use a 1″ socket or wrench to remove the lower tank fitting.  Next unscrew the knob that operates the valve, at the top of the tank.  My bike has what seems to be an “accessory knob” which isn’t listed in the parts manual.  Once the “accessory knob” is unscrewed, you will be left with two knurled fittings.  If you don’t have the “accessory knob”, then you’ll just have a screw which holds the top knurled fitting to the fuel rod.  The top fitting is pressed onto the end of the fuel rod and should pop right off.  The lower fitting is screwed into the tank and may need some careful persuading with a pair of pliers to loosen.  With the lower knurled fitting out of the way, you can remove any springs, washers or seals that are on the fuel rod.

Fuel Knob

The knurled portion under the knob is a separate piece, the knob screws into the end of the rod

Once all the parts are removed from the top end of the fuel rod, it can be dropped out of the bottom of the tank through the hole left by the lower fuel fitting.  To install the new fuel valve,  just  reverse the above steps.  Take note, that there is a small length of threaded rod which screws into the end of the fuel rod and is used for attaching the “accessory knob”.  You’ll need to reuse this piece from your original fuel valve, along with the knob itself, but everything else will be replaced with the parts from Carl’s Cycle Supply, including all the necessary seals.  As an added precaution, I used a dab of loctite blue on the threaded rod.  I hate to loose that knob on the road!

Side By Side Comparison

The top valve is the original, the lower is the replacement from Carl's Cycle Supply


Before installing the new parts, I took a few minutes to compare the new and old fuel valve.  My original fuel rod tip, had plenty of wear as well as some pitting.  No wonder I was getting the occasional leak.  Besides the difference in tips, the two fuel valves are identical in construction.  Every hole, thread, etc, matches up perfectly to the original.


Comparison of tips

The tip on the left is the new peek tip, on the right is the original metal tip

After everything is reassembled, don’t forget to reattach the crossover line to the right side tank.  Then make sure all your fittings are snug and refill the tanks with fuel.  My last step was adding a genuine Carl’s Cycle Supply sticker to my oil bag…

Be A Man

This sticker says it all...


Filed under Classic Motorcycle Maintenance, Panhead Jim's Blog, Tech by PanheadJim

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