Author Topic: gas tank size  (Read 1242 times)

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Offline waltcentral

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gas tank size
« on: July 11, 2019, 02:56:26 PM »
I assume my 1983 FLH has a 5 gal tank. The tank and tins appear to be new at some point. Tank has zero rust inside and inner fenders are clean. The service manual says:
FLH/FLHS.........TOTAL..........5 or 3.5 Gallons (US)
                       Reserve                    1.2 or 1 Gallons (US)

The bike has a Pingle petcock that goes on reserve around 2.2 Gal.
Looking inside the tank it is hard to tell how much fuel is left.  Are there any measurements I can do to the tank exterior to tell?

Offline david lee

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Re: gas tank size
« Reply #1 on: July 11, 2019, 06:03:24 PM »
drain it in to a container with measurements on it

Offline Hossamania

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Re: gas tank size
« Reply #2 on: July 12, 2019, 05:35:14 AM »
Bring along a measured amount of fuel, go for a ride, run it out, add the carry fuel, got to a station and fill it, and note how much fuel it takes.
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Offline 96flhpi

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Re: gas tank size
« Reply #3 on: July 12, 2019, 08:44:55 AM »
The Pingel on my 5 gal tanks goes to reserve at about 4 gal.  Try to find rider view pics of bikes with 3.5 vs 5 gal tanks itís easy to see the difference.  The fillers are much closer to the rounded sides on the 3.5s.

Offline waltcentral

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Re: gas tank size
« Reply #4 on: July 12, 2019, 11:22:36 AM »
My tanks

Offline Hossamania

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Re: gas tank size
« Reply #5 on: July 12, 2019, 11:53:38 AM »
They look like my old 4 gallon tanks on my '95 Heritage.
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Offline 96flhpi

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Re: gas tank size
« Reply #6 on: July 12, 2019, 03:56:55 PM »
Yeah Hoss they donít look as big as my 5 nor as small as the 3.5s.  You have a pic from a lower angle?  Often the fillers look a little tilted (not parallel with ground) on the 3.5, at least from the pics Iíve seen.

Offline waltcentral

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Re: gas tank size
« Reply #7 on: July 12, 2019, 06:13:34 PM »
not great pics but the fill caps do not really seem to angle out like some 3.5's

Offline waltcentral

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Re: gas tank size
« Reply #8 on: July 12, 2019, 06:15:12 PM »
other side

Offline One4Tone

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Re: gas tank size
« Reply #9 on: July 12, 2019, 08:54:19 PM »
if you have a working speedo..you can use the mileage as a guide...

Offline waltcentral

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Re: gas tank size
« Reply #10 on: July 13, 2019, 11:34:46 AM »
Rode today until reserve came on then 12-15 miles to the gas station. For the first time I opened both caps while bike on the jiffy stand I filled the left and capped it and then the right.
Took 4.2 gallons.
I assumed with the crossover I was good.  Good chance of 5 gal tanks.


Offline 96flhpi

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Re: gas tank size
« Reply #11 on: July 13, 2019, 06:17:54 PM »
Definitely 5s, which are rarely exactly 5 BTW.

Offline Hossamania

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Re: gas tank size
« Reply #12 on: July 13, 2019, 10:23:21 PM »
Rode today until reserve came on then 12-15 miles to the gas station. For the first time I opened both caps while bike on the jiffy stand I filled the left and capped it and then the right.
Took 4.2 gallons.
I assumed with the crossover I was good.  Good chance of 5 gal tanks.

The reserve on those tanks was 1/2 gallon, I believe. At 40 mpg, if you went 15 miles, you almost burned out all the reserve fuel (20 miles of reserve), so the 4.2 gallons you added was almost the maximum they hold.
No government, however well intentioned, can avoid becoming a tyranny.

Offline 96flhpi

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Re: gas tank size
« Reply #13 on: July 13, 2019, 11:25:58 PM »
My experience is reserve with a Pingel on 5 gal tanks is about a gallon.  IIRC with the original petcock reserve was less than a gallon.

Offline Hossamania

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Re: gas tank size
« Reply #14 on: July 14, 2019, 07:23:12 AM »
I forgot that it had a Pingel petcock, that will change the reserve from stock.
The only true way to know, run it completely out and fill it back up.
No government, however well intentioned, can avoid becoming a tyranny.

Offline fleetmechanic

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Re: gas tank size
« Reply #15 on: July 14, 2019, 11:50:08 AM »
The 3.5 gallon tanks were discontinued in the mid 1970s about the time the last hand shift versions were made in 1978.  We have a 1975 with 3.5 gallon tanks and handshift.

Offline david lee

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Re: gas tank size
« Reply #16 on: July 14, 2019, 06:23:19 PM »
The 3.5 gallon tanks were discontinued in the mid 1970s about the time the last hand shift versions were made in 1978.  We have a 1975 with 3.5 gallon tanks and handshift.
my 80 lowrider has 3.5 tanks

Offline 96flhpi

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Re: gas tank size
« Reply #17 on: July 14, 2019, 08:15:05 PM »
Fairly certain the FX models have the smaller tanks up to present.  I guess itís just tank now not tanks though.

Offline fleetmechanic

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Re: gas tank size
« Reply #18 on: July 15, 2019, 10:06:13 AM »
I should have said the 3.5 tanks were discontinued on the FL models.  But looking in the 41-84 parts book shows 1 # for 3.5 gal. tanks from '69-'77 and another # for 1978-what was then the present.  So I dunno.

Offline 96flhpi

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Re: gas tank size
« Reply #19 on: July 15, 2019, 01:17:18 PM »
Either way, tanks are easily replaceable and the 3.5 and 5 gal tanks for a 4 speed frame are interchangeable.  OP has a new to him 35yo bike.  Good approach not to assume theyíre 5 gal just because theyíre supposed to be.

Offline david lee

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Re: gas tank size
« Reply #20 on: July 15, 2019, 03:57:31 PM »
when i used to repair and paint harleys i used to widen tanks to take 7 gallons

Offline bump

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Re: gas tank size
« Reply #21 on: July 16, 2019, 04:10:14 AM »
Back in the late 70s early 80s Harley put 3.5 or 5 gallon tanks on different bikes. Not all flt had 5 gallon tanks and not all fx had 3.5. The tanks are interchangeable.

Offline david lee

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Re: gas tank size
« Reply #22 on: July 16, 2019, 04:06:04 PM »
new aftermarket tanks were crap and had to be repaired

Offline 76shuvlinoff

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Re: gas tank size
« Reply #23 on: July 16, 2019, 06:38:08 PM »
new aftermarket tanks were crap and had to be repaired

 The aftermarket tanks from Mexico on my 76 FLH have been patched a couple times. Trashed the originals in an incident in 2003.
Being defenseless does not make you more safe.

Offline david lee

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Re: gas tank size
« Reply #24 on: July 17, 2019, 03:56:12 PM »
new aftermarket tanks were crap and had to be repaired

 The aftermarket tanks from Mexico on my 76 FLH have been patched a couple times. Trashed the originals in an incident in 2003.
even used genuine are better