Gas tank and mileage

robs ss

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try https://www.nortonownersclub.org/node/2976

Look for the post where a MK1A and a MK3 were compared. MK1A was larger and wider at back unbaffled, MK3 was narrower at rear and baffled.
Yep - that's good
Tentatively (report by one person is not definitive IMHO) we would say:

SS & Highrider 9 litres
Roadster (GRP) 10 litres
Roadster (steel) 11 litres
Fastback 15 litres
LR Fastback 18 litres
Interstate MkIII (steel) 22 litres - to be confirmed
Interstate (GRP) 24 litres
Interstate Pre-MkIII (steel) 25 litres

Edit: The MkIII riders Manual (p5) states the interstate had 23.87 litres https://britmoto.com/manuals/Manuals/Riders_4.pdf

Cheers
 
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Good point re gearing - I'm a 19 tooth guy... ;) When I bought my current Commando it had a 23 tooth sprocket - it might have been able to manage 50MPG...if it had been on the bike any longer than the time it took to order/receive a 19T from Old Britts! :rolleyes:
 

maylar

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Good point re gearing - I'm a 19 tooth guy... ;) When I bought my current Commando it had a 23 tooth sprocket - it might have been able to manage 50MPG...if it had been on the bike any longer than the time it took to order/receive a 19T from Old Britts! :rolleyes:
My buddy's 72 Combat Interstate gets him 45-47 MPG, 19T. If I get less than 50 MPG on my 74 MKII with a 20T there's something wrong.
 
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how long is the stand pipe on your main fuel tap or is it missing oem was over 1 inch replacement taps may not have one that makes for a very small reserve ps you can get a couple more miles if you lay the bike over on the reserve side dont ask how I know
 
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Yep - that's good
Tentatively (report by one person is not definitive IMHO) we would say:

SS & Highrider 9 litres
Roadster (GRP) 10 litres
Roadster (steel) 11 litres
Fastback 15 litres
LR Fastback 18 litres
Interstate MkIII (steel) 22 litres - to be confirmed
Interstate (GRP) 24 litres
Interstate Pre-MkIII (steel) 25 litres

Edit: The MkIII riders Manual (p5) states the interstate had 23.87 litres https://britmoto.com/manuals/Manuals/Riders_4.pdf

Cheers
I just filled my freshly painted steel roadster tank today, after giving a small amount of petrol to ride to the service station, and it took 11.2 litres to fill.
 

Mart UK

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I have a '75 mkIII 850 roadster. Single Amal 34. 23 tooth gearbox sprocket. The factory Workshop Manual states 2.7 imp gals, 12 litres, 3.2 US gals. I calculated 68 miles per Imp gal on a semi spirited ride on Friday (self limiting to 5,500 rpm). I will allow for not quite judging brim to brim levels, but likely north of 60mpg. I did 120 miles of mostly twisty back roads, without hitting reserve.

For a Mk III the Workshop Manual states:
Fastback = 15 litres
LR Fastback = 18 litres
Interstate = 25 litres

Does anyone have a neat, safe way to carry a litre of fuel, for emergencies?
 

L.A.B.

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I did 120 miles of mostly twisty back roads, without hitting reserve.


Have you checked which is 'main' and which is 'reserve'?
Reserve would normally go on the left on a Mk3, however, the earlier models had reserve on the right so the taps can be swapped over to suit rider preference.
A small quantity of fuel often remains trapped on the main side after reserve has been drained and the bike then has to be tipped on its side so the trapped fuel sloshes over to the reserve side of the tank although that last drop of fuel won't get you very far.
Some owners prefer to fit two reserve taps.
 

Mart UK

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Have you checked which is 'main' and which is 'reserve'?
Reserve would normally go on the left on a Mk3, however, the earlier models had reserve on the right so the taps can be swapped over to suit rider preference.
A small quantity of fuel often remains trapped on the main side after reserve has been drained and the bike then has to be tipped on its side so the trapped fuel sloshes over to the reserve side of the tank although that last drop of fuel won't get you very far.
Some owners prefer to fit two reserve taps.
Sadly, I got to know my fuel taps intimately, whilst checking the fuelling / carbs recently!
 

Tornado

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Beware if using the speedo trip or odo to make you fuel mileage calculations. These can be inaccurate to some degree. Should confirm both the speedo and odo readings with a GPS. I use my cell phone with a mapping app to check these. I also have a vehicle fuel mileage logger app which lets me punch in litres added at a pump and the distance since last fill up. Mileage then logged and can be graphed with all previous data point for later review.
 

RoadScholar

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If you do run out of fuel while on your reserve tap you can get a few more miles by tipping the bike such that the main tap side of the tank flows what is left there into the reserve side. You may have to lay it down flat, possibly a bit more, so watch the time as the oil tank may want to participate. This procedure should be considered a "last resort", and as noted above, you must have the physical capacity to right the bike.

If you have the tools aboard removing the tank and turning it to the reserve side is more time consuming, but much safer and won't rook your back.

Carrying additional fuel is not uncommon, especially if you have the luggage rack option. The container must be approved and strapped down securely. I, personally, don't advise this. If you get hit from the rear on a warm to hot day (any day really). The extra fuel will give you all the miles needed to get to a meeting with your maker.

The better bet is to drain the main tap with drive line at operating temp and have someone follow you until you run out of motion lotion, note how far you got, decrease the distance by 25% and you'll know what the reserve can do. If you are too far from a refueling point at least look for a place where you can get a decent cell signal.

Best
 

Tornado

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My auto club membership covers me for emergency fuel (1 US Gal.) delivered by roadside assistance truck. I have on occasion carried 1 litre in alu fuel bottle (also doubles as camp stove fuel bottle....my stove can also burn gasoline). There are fancy/stylish holsters for these cylindrical bottles made for motorcycles...some in vintage looking leather....can also hold drinking water vessels. I just put mine in my pannier on my Bonneville. Don't have a carrier on the Norton yet.

But realistically, if you are running out of fuel from a full tank, esp an interstate tank, not sure how you can ride for 1.5-2+ hrs without taking a break. That's my signal to stop for fuel ups. I've not run out on my trips with the HiRider 9 litre (about 80 miles range) tank yet....
 
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Derek Wilson

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My Combat goes about 150 miles on the alloy FB tank, before going on reserve. Fill up is around 16 litres. Reserve is a bit paltry, luck if it will go another 10 miles after hitting reserve.

I never calculate mileage... It is all about the smiles per gallon :cool:
 
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