Expected MPG

Okay, I'm done searching this forum; what's a reasonable expectation of mileage to be seen with a stock, reasonably tight engine out on the interstate? '74 850 Interstate, to be specific. To the best of my knowledge, it's running stock gearing (21?/42). Nathan

45-50mpg on Amals, depends on riding style and US gallon is smaller than our real gallon..

If you're going to pull the "Imperial" card, why not go km/litre? :roll: Anyway, thanks for confirming my suspicions. I figure a 6+ gallon tank should get me down the road quite nicely. That's not to say that I could sit the old girl for 300 miles...

On my trip to the NOC rally in France last week, mine returned 57 mpg (Imp) / 47.5 mpg (US) / 5l/100km

This was with camping gear on the back and a fair amount in waterproofs. The consumption will have been helped by the proliferation of speed cameras in France and very strict limits in built up areas (with an mph speedo, I was erring on the slow side).

I put in about 1/2 pint (imp) of oil over the 850 miles.

I grew up with pounds and pence, feet inches and thou's. Then at University (and since) it was MPa and GPa or MN/m2 for stress, E (modulus) etc. I never use psi for stresses as I only know material values in MPa/GPa but have to then back convert MPa to psi to get a understanding of unit loading i.e 2psi is a bag of sugar sat on an inch. I can't see that with MPa. Confused.com.

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FastFred said:

I grew up with pounds and pence, feet inches and thou's.

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This reminds when the Uk went 'metric''.
Someone, widely quoted in the press, put out a note for the milkman, asking for 1136 mls of milk.
Next morning, no milk.
When questioned the following morning, said 'didn't know what that means. ?
2 metric pints was the answer....

My petrol tank was made in gallons, and the speedo in miles.
Easy to figure things out from there.
10km/litre = 10 litres/100 km = 28 mpg
56 mpg is 5 litres/100km.

Checked mine over 3 tankfulls last year, lot of 2 up riding & twin Amals.
Averaged out at 60.5 miles to the gallon.

Averaging out decade+ of asking all sorts and reports online a decent Commando should get about the same as a decent Harley, ie mid 50's mpg. WOT raced Cdo and get into the low 30's mpg and a leaned out tall geared legal ridden can Cdo touch 70. This is for the 400 to 1800 ft elevations of course between temperatures water is a solid or steam.

I had Peel in perfect fit for me resting on big tank bag that 300 miles of pure road trace only aware of eye balls and grinning was not nearly long enough to savor all at once. I tell you what 6 gallons sure helps being brave taking off the beaten path not knowing when it when it will let out again or even all the way passable but able to just turn around with enough to spare, enjoy how far away ya got instead of cursing it.

When I ran a 24-tooth front on my 850 for a while, I was getting about 55-60 mpg on highway trips. It's a 15,000-mile engine in good shape and runs on Amal Premiers, a stock airbox and a Trispark ignition.

I switched to a 23 and it's more like 50-55 on the highway and mid-to-high 40s snapping around town.

I get 50-55 mpg (US gallon - no ethanol fuel) with a single 36mm Mikuni and 22 tooth drive sprocket

The roadster tank is damned small for any touring. At high speed on the interstate going with 70-80mph traffic I think you would be very lucky to get 50mpg, and you would be very wise to watch the odometer closely and stop for fuel every 60 miles until you got used to what your bike used.

When I was young and going on longer trips with my 850 Roadster I had a heavy right hand and I don't think I got better than 35mpg. I ran out of fuel more than a few times with that bike.

I do very little highway riding. Mostly backroads in the 50-70mph range. I have an app on my phone and have tracked it for just over 100 gallons and have gotten almost exactly 40mpg. I hit reserve at about 80 miles and usually takes exactly 2 gallons.

1974 Roadster with a Pazon Sure Fire and a single 34mm Mikuni.

I did 400 miles yesterday and 400 on Friday. Speeds were 70 -75 thru the mountains. My fuel mileage was right around 50 Imperial, or about 40 US. On other runs at 60 mph without the full bore runs uphill in the passing lane, the bike has done over 60 Imp. So there are lots of variables, headwinds being one of the biggest.
One of our group was riding an 850 MV Augusta, a very expensive and exotic piece of machinery. It ran out of fuel just the same as any other bike will and got refueled roadside from the Norton Interstate Mothership. After that I was feeling quite chuffed until the battery went flat and the bike died about two hundred and fifty miles from home. Luckily I was able to coast into into town and park in the DQ parking lot while friends purchased a new Yuasa 14 amphour battery for the Norton.
Ran dead loss all the way home and it still has good voltage (Boyer ignition). When the bike first lost spark, I put in the spare fully charged new Ballistic 12 cell that I had on board. That only made it 50 miles before going flat. If I carry a spare battery in the future it will be a new or near new lead acid.
Bike used about 8 ounces oil, no visible leaks. I'm happy with that.

Glen

I have done several interstate trips running 70-75MPH on a roadster tank. ALWAYS have gotten over 50 MPG hit reserve around 135 miles but make it a practice to fuel up around 125 miles. this is with a combat, 32 amals and 21 tooth sprocket.I still avarage over 50 MPG with the riding around in the mountains that I do .

beng said:

The roadster tank is damned small for any touring. At high speed on the interstate going with 70-80mph traffic I think you would be very lucky to get 50mpg, and you would be very wise to watch the odometer closely and stop for fuel every 60 miles until you got used to what your bike used.

When I was young and going on longer trips with my 850 Roadster I had a heavy right hand and I don't think I got better than 35mpg. I ran out of fuel more than a few times with that bike.

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45 mpg - '72 combat with stock gearing and 932 Amals.