Capcity of various Interstate Tanks

bpatton · Jun 23, 2009

I just filled my Interstate tank from nearly empty to full. 6 gallons at Costco, USA. Can that be right? I've always thought 5gal, (US), was the bigger of the Interstate tanks. What sizes did they make?

Fullauto · Jun 24, 2009

Sounds about right for a steel tank. The 750 fibreglass ones were smaller. By how much I can't remember. Matt Rambow gave up supplying Corbin seats for Interstates because he'd come across about six different shapes/lengths.

BillT · Jun 24, 2009

Steel Interstate tank : 5 1/2 Imperial Gallons (25 litres)

Right out of the technical data page in the manual.

5 -1/2 Imp. gallons is equivalent to 6 - 7/8 US gallons.

L.A.B. · Jun 24, 2009

The 750/850 Commando Riders Manuals list the Interstate tank size as "5.84 Imp. (7.3 US) gallons, 26.57 litres"

The 850 MkIII Riders Manual lists the Interstate tank as "5.25 Imp (6.3 US) gallons, 23.87 litres" as the later Interstate tanks were slightly slimmer I believe?

splatt · Jun 24, 2009

While on the subject,are all steel interstate tanks quite flexible in the main panels,if you grab the filler spout can you flex the top panel,or is it just mine , it may have been panel beaten and filed thinner. :roll:

Robert_Norton · Jun 25, 2009

L.A.B. said:
The 750/850 Commando Riders Manuals list the Interstate tank size as "5.84 Imp. (7.3 US) gallons, 26.57 litres"

The 850 MkIII Riders Manual lists the Interstate tank as "5.25 Imp (6.3 US) gallons, 23.87 litres" as the later Interstate tanks were slightly slimmer I believe?

The early Interstate tanks in fiberglass and steel were substantially wider than the later ones. From one of the 1974 sales brochure (if there was more than one), you can see the switch to the narrower style tanks had already occurred.

I believe there would be only three different styles; the largest in steel and fiberglass, and then the slimmer style in metal.

Going strictly from memory, since I have neither tank at this time, I would say the difference in width across the top panel between the two designs was at least two inches, and could have been as much as four inches(or more).

Alan W · Jun 26, 2009

by L.A.B. » Wed Jun 24, 2009 11:30 pm

... the later Interstate tanks were slightly slimmer I believe?

If this helps, my friend has had his Interstate since new (1977), and it definitely has the wider tank version (and is original), it is wider than my Interstate tank which I think is an aftermarket one fitted by a p.o.

worntorn · Apr 23, 2015

My 75 MK3 has it's original Interstate tank and it holds just under 24 litres, the number Les provided. To my eyes this version is slim enough to look good and still holds lots of fuel.
I did a 230 mile trip on Sunday and filled up afterward, 18.3 litres. This works out to approximately 57 miles per Imperial gallon.
So the range with about one gallon or 57 miles remaining for safety is 250 miles. Run dry would be right around 300 miles.

Last summer I met a fellow who tours on his 1974 Roadster. His wife rides pillion and the bike is loaded with camping gear. They have run the bike out of fuel at 90 miles, so now start looking for fuel every fifty miles. As he explained, you start looking at fifty rather than at 80 because there might not be any fuel available at 80 or even 90 or 100.
Seems like he needs an Interstate tank. All things considered it would increase his range from 50 to 250 miles or thereabouts.

Glen

Nater_Potater · Apr 23, 2015

BillT said:
Steel Interstate tank : 5 1/2 Imperial Gallons (25 litres)

Right out of the technical data page in the manual.

5 -1/2 Imp. gallons is equivalent to 6 - 7/8 US gallons.

'74 Interstate owned since new, so original tank. Runs 300 miles at 57-58 mpg and still doesn't hit reserve. No chance of body waiting for fill-ups as gauge for potty break.

splatt said:
While on the subject,are all steel interstate tanks quite flexible in the main panels,if you grab the filler spout can you flex the top panel,or is it just mine , it may have been panel beaten and filed thinner. :roll:

NO! I always was impressed/dismayed at just how massive the empty fuel tank felt in my hands, as if it was made out of recycled boiler plate. Be careful with that.

Nathan

bill · Apr 23, 2015

sounds more like a tuning issue then a roadster tank size. you should be able to get 50 + MPG US at a cruse speed of 70 MPH even wit a set of twin amals.

worntorn said:
Last summer I met a fellow who tours on his 1974 Roadster. His wife rides pillion and the bike is loaded with camping gear. They have run the bike out of fuel at 90 miles, so now start looking for fuel every fifty miles.

Glen

worntorn · Apr 23, 2015

He is 6'4, his wife is 6'1 and they also carry camping equipment including 2 lawn chairs. Quite a load.

motoalchemist · Apr 23, 2015

I usually pump 5.5 Gallons in mine....BUT i never fill mine all the way up because I have never fixed the seal around the filler cap. If I top off the tank, the first hard stop and half a gallon of gas sloshes out the fill cap. So I am sure once i fix this and I top off my tank..theres no reason why I couldnt get 6 gallons into this tank.

peter12 · Apr 24, 2015

I agree with Nathan, have had three Interstates, the tanks were all as strong as houses.
I did a considerable amount of work on the first two and had no flexing issues whatsoever.
Personally I would have though it would have taken an extreme amount of sanding to weaken them.

Personally I would like to streamline mine and revert to Roadster trim but the meagre capacity makes no sense to me at all!

Per G · Apr 24, 2015

There seems to be a great variation of Interstate tank sizes.
I have a -74 MK2A with what I believe is an original tank (steel).
It takes over 27 liters. I know because one time I filled just over 27 liters and it was still running when I got to the gas station

I get at least 600 Km touring range on one tank.

Regards
Per

Anglophile · Apr 24, 2015

I have a later model [double pinstripes] interstate tank (actually contemplating a return to the roadster tank) anyway, it's at least a six gallon (US) tank. I've done 300 miles between fill-ups.

Norton Dave · Apr 24, 2015

Just for the record Interstate tank capacity for the MK3 was 6.3 gallons ( 24 liters ) fiberglass tank and 6.6 gallons ( 25 liters ) for the steel interstate tanks .With the SS Hi Rider being the smallest capacity at just 2.4 gallons (9 liters ). I recall getting around 320 miles one up on a full steel interstate tank on the MK3 on a long run but it was completely empty then .

Capcity of various Interstate Tanks

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