Techline-Nov09-A TACH, A STUMBLE, AND A CLICK-Part II-Concludes

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This article concludes here.

The recall does not apply to California models because the vapors don’t feed into a fitting in a frame member on these bikes, but to the charcoal canister. Furthermore, the recall does not apply to EFI-equipped motorcycles because carburetion exclusively serves the FXRs, Dynas, and Softails in these years.

The possible obstruction in the vented gas tank connector is plastic. The factory estimates that perhaps this situation affects only 8 percent of the recalled bikes, but better safe than sorry. H-D is checking the other 92 percent of the bikes recalled to ensure servicing of all affected bikes. Furthermore, Father Harley laid down the law once again to its dealer network, telling members to perform the service whether they sold the bike or not. In my opinion, H-D is demonstrating real corporate responsibility here.

To fix a plugged gas tank vent line connector, first straighten out a large paperclip, one with a diameter of about 1/16". Using wire cutters, snip an end at a 45-degree angle to ensure it’s sharp. Bend one end of the extended paperclip inward about 1-3/4" to the longer piece if fixing a Dyna or FXR. Bend the end a shorter distance because of space restrictions if fixing a Softail. Next, take a 1/16" drill bit and some masking or electrical tape. Fold the sticky side over the drill-mounting end of the drill bit and stick both sides to each other. This will prevent the drill bit from dropping into the frame member, particularly on the Softails.

Stand on the left side of the bike and locate the vapor tube vent line. Disconnect this vent line from the vent fitting in the downtube frame member above the passenger footpeg on Dynas. The FXR vent tube fitting is on the left side of the bike at the rear of the lower frame cross member. Following the vent line makes these easy to spot. On the Dyna or FXR, insert the long end of the paperclip into and through the connector. If there is no resistance, the motorcycle has not been affected; continue anyway, since it is better to be safe than sorry. Push the paperclip in with enough force to puncture the plastic flashing. Run the clip back and forth, opening and enlarging a channel through the flashing.

Insert the 1/16"-drill bit into this opened channel and run it back and forth while running the bit through your thumb and forefinger to approximate a drilling action. This will ensure the channel is open and clear. On Softails, remove the two bolts and their respective flat washers to release the bottom, black, molded extension of the rear fender in front of the rear wheel. Bend this flexible piece back to the wheel and hold it there. At the rear of the shock mount, on top of the rear swingarm, is the vent fitting. Again, it’s easy to locate if you follow the vent line.

Remove the vent hose from the fitting. Repeat the above procedure except insert the short end of the sharpened paperclip. Space restrictions require this. This is also where the masking tape comes in handy to prevent the drill bit from falling straight down through the vent fitting into the swingarm. However, if it falls in, it’s no big deal except for losing a drill bit. Reattach the fender extension. Always use red Loctite along with specified torque values, as vibration is very efficient at loosening unsecured bolts and nuts.

Venting Necessities
The gas tank and the fuel delivery system venting are essential for the gas to flow out of the tank via gravity and into the carburetor. In bikes equipped with electronic fuel injection, gas feeds under pressure via an internal fuel pump inside the gas tank. Excess gas returns (pumps) to the tank.

The gas tank still needs venting to let air in to fill the space left by the exiting gasoline. The pump will override some of the laws of physics for a time, but the system will begin to suffer the consequences of any physical violations. There have always been venting problems; sometimes a blocked-by-dirt vented gas cap prevents air from entering the gas tank. On a carbureted bike, the gas cannot exit the fuel tank via the gas petcock if the vent is blocked.

Carburetors are all about the laws of physics. Air must flow back into the tank through the vent from outside the tank. Dual tanks, like those used on Evo Softails, also had two connecting hoses between the tank halves. There is one at the bottom front of the tanks, which allows fuel to flow from one tank to the other so that each tank will have the same amount of gas in it when the bike is vertical. Of course, when on its sidestand more gas will flow into the left tank as the liquid seeks to level. Atmospheric pressure will force the higher level of the gasoline on one side of the tank to enter the lower side until atmospheric pressure equalizes in both tanks. This principle of equalized pressures is why a liquid will always seek its own level. A simpler way of looking at it is the weight of the gasoline over the exit connecting hose creates enough pressure to force gas through the hose until the weight (pressure) equalizes in both tanks. Harley-Davidson takes advantage of this physical principle to utilize only one outlet for two separated gas tank halves. The gas only flows out of the petcock located in the left tank, at the rear, near the bottom. The right tank needs to empty and equal its reservoir with the left one to keep a constant supply of fuel on hand.

This equalization hose is also required on single gas tanks if they have a hump in the middle so that the tank will fit over the top frame member. If this hose is necessary then a vent will be also. The gas cap, if vented, will satisfy the demand in this particular case if air can flow over the internal hump. If not, then a vent line between the tanks will be necessary. Between split tanks, the vent line travels from one tank to the other at the top front just forward of and below the speedometer. The speedometer housing hides the vent line from view.

When troubleshooting a vent problem on a dual split tank system, ensure the gas cap vent is okay. I always ask the owner if there is a recent removal and reinstallation of the gas tanks. If so, dollars to doughnuts, my money says that the wrench kinked this line. It is normally problem free once properly installed and then left alone; but Harley riders are always taking their gas tanks off for one reason or another. Identifying and tracing symptoms, as well as applying logic to a wide knowledge base, will lead the thinking mechanic to the cause, and thus the fix. Thinking is the key word. Those that do not think a problem through inevitably attempt to patch a symptom, not fix the cause.

Diagnosing Gas Overflow
I will state the obvious: gas overflow is dangerous, especially on a hot bike. With diagnosis of any problem, I always examine inexpensive and easy fixes first, and progressively expand to more expensive and difficult solutions. This practice will save much money and effort. For example, if a customer complains of an engine knock, I will not tear down the engine as the first option. Many shops will.
Do the free things first, taking advantage of your senses. Actually, this is very wrong. First comes safety. Grab the fire extinguisher and have at the ready. Move the bike into the open air if in a confined space, like a garage, or around other expensive motorcycles and machinery. Ensure there are no sources of ignition. If the bike is running, turn it off. If anyone is smoking ask him to leave the immediate area.

The next thing to do is isolate the problem. If the bike has a manual or vacuum-operated petcock, turn it to the off position to starve the problem in case the gas leak is downstream of the fuel tank. Observe the problem area. If gas is overflowing on the bike, look at the fuel tank, fuel tank fittings and lines, the induction system (carburetor or EFI), as well as connecting or linking parts such as vent lines and the vapor valve. A sense of smell will indeed confirm overflowing gasoline, an overworked clutch, or a rubbing tire to name a few examples. Touching will confirm whether gasoline overflow originates in an area that the mechanic cannot readily see, like from a split weld underneath the gas tank. Turn the radio off and listen. You can hear gas dripping on a hot exhaust pipe and perhaps smell it. You can also hear escaping gas venting. Thus, the initial diagnosis does not involve any tools whatsoever, especially expensive specialty diagnostic ones. Therefore I smell, look, listen, and feel for problems. Where I begin will depend on the
customer complaint.

Conclusion
Next month we’ll get into Evo petcocks.

Donny Petersen
Tattoo Tony’s Heavy Duty Cycles
Toronto, Canada
www.HeavyDutyCycles.com