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?
drain it in to a container with measurements on it
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.
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 it's easy to see the difference. The fillers are much closer to the rounded sides on the 3.5s.
My tanks
They look like my old 4 gallon tanks on my '95 Heritage.
Yeah Hoss they don't 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 I've seen.
not great pics but the fill caps do not really seem to angle out like some 3.5's
other side
if you have a working speedo..you can use the mileage as a guide...
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.
Definitely 5s, which are rarely exactly 5 BTW.
Quote from: 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.
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.
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.
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.
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.
Quote from: 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.
my 80 lowrider has 3.5 tanks
Fairly certain the FX models have the smaller tanks up to present. I guess it's just tank now not tanks though.
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.
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 they're 5 gal just because they're supposed to be.
when i used to repair and paint harleys i used to widen tanks to take 7 gallons
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.
new aftermarket tanks were crap and had to be repaired
Quote from: david lee on July 16, 2019, 04:06:04 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.
Quote from: 76shuvlinoff on July 16, 2019, 06:38:08 PM
Quote from: david lee on July 16, 2019, 04:06:04 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
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.
I fill them full of water and weld them.