Fuel Cap gasket replacement?

[ksw92]

It finally got warmish here in the City of Angels. On the sun-baked ride home today I noticed a pretty strong raw-fuel smell coming up at me while at stoplights. A quick sniff test when I got home let me to the filler cap. The tank was a little less than half full and warm to the touch due to the sun. Usually, that'll result in a little pressure buildup in the tank but I got nothing when I opened the filler cap. The gasket seems like its in good shape (pliable, no cuts or anything) but given the age I guess its shot?

I quick search doesn't seem to turn up any replacement gaskets, just the whole cap. Anyone else have that experience yet?

 

[SMSW]

I think the cap is vented, is it not? So you will get the occasional whiff of gas. Perhaps I should amend this. My aftermarket (Oberon) keyless screw in gas cap IS vented - I can see the hole - and I do smell gas now and then. IIRC, dropping my bike on a full tank with the OEM locking cap did not leak. It does weep slightly (but not from said vent) with the aftermarket cap. Now that I think about it, the OEM setup uses a charcoal canister to trap fumes, so it must be sealed - i.e. vented through the canister.

 

[CYYJ]

There are a whole bunch of hoses under the gas tank of the ST 1300, for venting, draining, and emission control.

You might want to tilt the fuel tank up and have a look to confirm that all of the hoses are still properly connected. The photo below shows where they are, looking towards the rear of the bike.

While you are in there, carefully inspect the L-shaped hose that connects the upper fuel tank to the lower fuel tank. You can see it just below dead-center of the photo. That hose has been known to fail, and the results can be catastrophic if it fails (bike catches fire).

Michael

Vent & Drain Hoses - ST 1300 Fuel Tank

 

[ksw92]

Thanks, CYYJ, I'll check the under-tank evap hoses. The OEM design has an evap system so I guess I'll need to check that as well. It was pretty obvious to me that vapor was leaking out around the filler cap. Time to crack open the service manual...

 

[ST-Traveler]

It was pretty obvious to me that vapor was leaking out around the filler cap.

I have not experienced this since owning my ST1300 some 10 years.

 

[CYYJ]

KSW:

Here's a link to a related discussion that might be of interest to you. My thinking is that maybe the drain hole at the perimeter of your fuel cap is blocked, and a wee bit of fuel was accumulating in the drain up by the cap, rather than running down the hose and out onto the ground like it should.

Tank venting issue/charcoal canister?

Michael

 

[Igofar]

Check out post #5 in the link that Michael was kind enough to attach.
I'm guessing this may be your problem as well....I've found this pretty common on the ST1300's.
Let us know what you find.
Larry

Find the cause of the failure, instead of throwing solutions at a problem

 

[ksw92]

Thanks for the pointer. That thread is a good reminder to not assume the first part you think of is faulty. Guess I'll be pulling some tupperware this weekend.

 

[CYYJ]

KSW:

If you sequence your troubleshooting & fault-finding activities correctly, you might be able to solve your problem with no Tupperware disassembly at all.

Here is how I suggest you approach fault-finding... you will need a 5 mm hex key and a 20 cc plastic syringe. You can get the syringe at any drugstore for about $1 - you don't need a needle on the end of it, just the plastic syringe.

Put the bike on the side-stand, then, release the gas cap by unlocking it. Now loosen and remove the three hex-head bolts that hold the gas cap assembly in place. There are 7 bolts around the perimeter of the gas cap, but only 3 of them are used to hold the gas cap onto the tank. These are highlighted with green arrows in the picture below.

Once you have the gas cap assembly off, clean up the recess in the top of the tank - get rid of all the dirt & crud in there. Now fill the syringe with some warm soapy water, and fill up the 'moat' around the hole in the top of the gas tank. If the drain hole is free and clear and no hoses are kinked or blocked, the water will drain quite quickly out the bottom of the motorcycle. I think that the drain hose is the shorter one identified by the arrow on the left of the second picture.

If the water does not drain, or drains slowly, manipulate the end of the drain hoses under the bike, you might be able to clear a blockage if the blockage is at the end of the hose.

If no luck, then you will need to lift the gas tank and see if the blockage exists in the tank itself (in the metal tube within the tank that leads from the drain hole to the outlet labelled 'DRAIN' in the picture in post #3 above), or if the blockage is in the hose that connects to that outlet. Disconnect the hose from the DRAIN outlet, and use the syringe to squirt a little soapy water into the drain inlet up by the gas filler hole - see if that metal tube is blocked or not. If it is not blocked, then use the syringe again to squirt water down the rubber hose. If you don't get any water coming out the bottom, investigate the hose run for kinks or blockages.

Save the syringe for later use - it is very handy to have one around for emptying brake and clutch fluid reservoirs, etc.

Michael

Gas Cap
Green Arrows highlight the "real" fasteners to remove - the other 4 are just decorative, don't try to undo them!


Drain Hose Outlets