HarleyTechTalk

Technical Forums => Shovel Head => Topic started by: waltcentral on July 11, 2019, 02:56:26 PM

Title: gas tank size
Post by: waltcentral 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?
Title: Re: gas tank size
Post by: david lee on July 11, 2019, 06:03:24 PM
drain it in to a container with measurements on it
Title: Re: gas tank size
Post by: Hossamania 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.
Title: Re: gas tank size
Post by: 96flhpi 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.
Title: Re: gas tank size
Post by: waltcentral on July 12, 2019, 11:22:36 AM
My tanks
Title: Re: gas tank size
Post by: Hossamania on July 12, 2019, 11:53:38 AM
They look like my old 4 gallon tanks on my '95 Heritage.
Title: Re: gas tank size
Post by: 96flhpi 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.
Title: Re: gas tank size
Post by: waltcentral 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
Title: Re: gas tank size
Post by: waltcentral on July 12, 2019, 06:15:12 PM
other side
Title: Re: gas tank size
Post by: One4Tone on July 12, 2019, 08:54:19 PM
if you have a working speedo..you can use the mileage as a guide...
Title: Re: gas tank size
Post by: waltcentral 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.

Title: Re: gas tank size
Post by: 96flhpi on July 13, 2019, 06:17:54 PM
Definitely 5s, which are rarely exactly 5 BTW.
Title: Re: gas tank size
Post by: Hossamania 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.
Title: Re: gas tank size
Post by: 96flhpi 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.
Title: Re: gas tank size
Post by: Hossamania 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.
Title: Re: gas tank size
Post by: fleetmechanic 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.
Title: Re: gas tank size
Post by: david lee 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
Title: Re: gas tank size
Post by: 96flhpi 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.
Title: Re: gas tank size
Post by: fleetmechanic 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.
Title: Re: gas tank size
Post by: 96flhpi 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.
Title: Re: gas tank size
Post by: david lee 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
Title: Re: gas tank size
Post by: bump 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.
Title: Re: gas tank size
Post by: david lee on July 16, 2019, 04:06:04 PM
new aftermarket tanks were crap and had to be repaired
Title: Re: gas tank size
Post by: 76shuvlinoff 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.
Title: Re: gas tank size
Post by: david lee 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
Title: Re: gas tank size
Post by: crock on July 18, 2019, 04:33:53 AM
mine started leaking from the tabs years ago. converted to flat sides and love them. Have an OE set  that are mix & match Bought em from an ini off wrecks. Left side from one and right from another.
Title: Re: gas tank size
Post by: dirtymike on July 19, 2019, 08:32:23 AM
I fill them full of water and weld them.