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Gas tank caps interchangeable?

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Gas tank caps interchangeable?


Post by panz4ever » Sat Mar 22, 2008 11:26 pm

Should 65 gas tank caps be interchangeable? Was on another forum and a guy posted that all panhead tanks use two interchangeable vented only caps. Thought one was and one was not.

And my two tanks caps are defintiely not interchangeable. If you look inside the tanks one side has a longer throat (for lack of a better word) and one cap is longer than the other to accommodate the tanks.

I have owned the bike since 1970, and other than paint and tires it is original..from what I can tell and have read about her.

And if it makes a difference, the tanks are the 5 gal foot shift.

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Post by Cotten » Sun Mar 23, 2008 12:25 am

My '65's 3.5 gallon "gated" tanks have interchangeable caps, but I believe all 5 gallon tanks were not.


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Post by john HD » Sun Mar 23, 2008 2:33 am

i have a set of later 60's 5 gal. tanks that use different caps. no gate.

they do not have the instant reserve and have the petcock on the rear of the left tank.

i think someone told me they were '66 to '69 tanks.


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Post by Cotten » Sun Mar 23, 2008 2:44 am

Early '66 tanks had the modern petcock on the right tank, both 3.5 and 5 gal models.
My best recollection (usually faulty) is that the caps upon the 3.5s were the same.


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Post by john HD » Sun Mar 23, 2008 3:27 am


you memory is correct, a very good friend of mine has a early 66 with 5 gallon tanks. the petcock is as you describe. perhaps the set i have is 67 to 69 now that i think about it.

now all i have to do is look at his tanks next time i see him.

he IS a big fan of your floats btw...


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Post by DuoGlide62 » Sun Mar 23, 2008 12:36 pm

The reason for both tanks having vented caps has to do with,... are ya ready ? ... venting. If your tanks have the top crossover line, (check under the dash cover, in front of the speedo) you only need the vented cap on the right tank. If there's no crossover vent line,.. you need both caps to be vented.



Post by Guest » Sun Mar 23, 2008 5:18 pm

When both caps are vented, Is there any way of stopping the fuel leakage out of the left tank cap caused by the higher tank bleeding fuel to the lower tank while tanks are full and bike is on the jiffy stand?

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Post by 51Hog » Sun Mar 23, 2008 5:21 pm

Sorry bout the double post. That was me not logged in.

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Fuel Tanks


Post by drinner-okc » Sun Mar 23, 2008 5:51 pm

If you still have the original style shut-off valve (pull up for reserve) when
you screw down the rod it should seal both ways, fuel going out of the tank, and fuel trying to balance out. I know that even the best of them
will bypass some. The aftermarket parts are nearly impossible to seat.
If you have had the tanks off and made any changes, even a paint job
where you worked any dents, find the tool to "align" the top & bottom
holes, and "adjust" the distance. I did mine without hitting the tool, as it
was new & not mine. Mine lacked about 1/2 turn seating before the knob
hit the top of the tank, I simply put a spacer twice as thick as I needed
between the valve body and tank & screwed the tool in. The "memory" of the metal brought it back just right after about 2 or 3 trys with different
amouts of shimming. Didn't even stress the paint.
Use Linkert bowl washers (copper) instead of brass washers that were OEM. They crush & seal better so no drips on footboards.
If you have Petcock style tanks (later year or A/M) you'll need a non-vented cap on the left side.
I alway part my bike on the "Bates Ride-Off Stand" so the tanks are
level anyway. RUB's are always wondering how my bike stands up straight. That's best accessory I ever bought! drinner-okc



Post by Guest » Mon Mar 24, 2008 3:16 am

Guest, yes, don't fill it all the way. Mike

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Post by FlatHeadSix » Mon Mar 24, 2008 4:50 am

All the stock 3.5 gallon tanks had interchangeable Eaton caps, it was the rider's option to put an unvented cap on the left side to prevent fuel from cascading down the side of the tank when both tanks were full and the bike was on the jiffy stand.

There is no way to stop the transfer from one tank to the other when the bike is parked, it would defeat the purpose of the crossover if there was. The "instant reserve" shutoff only prevents fuel from flowing down to the strainer at the carb, it will not stop fuel from flowing through a vented cap when the fuel level is high enough in the tank to get by it.

If you want fuel in the carb when you ride the bike the crossover has to be free to transfer fuel from one tank to the other and at least one cap has to be well vented so it will pull enough air to prevent the tanks from pulling a vacuum.

Trying to crack a cap a 70 mph when the engine dies so that the tank can gulp some air and send some more fuel to the Linkert is dangerous (and not fun either), put the correct vented caps on the tank and worry about something else!


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Post by VPH-D » Tue Mar 25, 2008 4:04 pm

The 65 and later 5 gallon tanks use 61103-65 non vented left cap.
The 66 and later 31/2 gallon tanks also use this cap.

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