Author Topic: MPG  (Read 1766 times)

Offline Mosin

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MPG
« on: 22.06. 2010 11:47 »
I'm just wondering how many miles people expect to get from a tank of petrol? Obviously there are loads of variables, but what would people expect to get? Personally, I make a point of trying to fill up every 100 miles. This is mostly because I am slightly dubious about what may be lurking in the bottom of my tank and I've an inline fuel filter fitted on the main fuel tap but not on the reserve one so I try to avoid using reserve if at all possible. Having sone 100 miles, it usually takes about 15 litres to take me back to full. I'm happy enough with the, but is it about the same as other people are getting?

Simon
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England

Offline MG

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Re: MPG
« Reply #1 on: 22.06. 2010 11:58 »
15 litres is about the full capacity of the 4 gallon home version tank. This would mean you have about 25mpg, which definitely is NOT good fuel economy.  *eek*
I usually get around 180-200 miles out of one tank easily, although my carbs are jetted on the rich side to avoid pinking and improve internal cooling. This would be around 45-50mpg, sometimes less when thrashed or riding two up naturally.
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Offline Beezageezauk

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Re: MPG
« Reply #2 on: 22.06. 2010 19:14 »
I agree with MG.

Motorway touring and riding solo with camping gear gives me 200 miles without going onto reserve with the B31 but the A10 can't quite manage that figure.  Without going onto reserve I refill the A10 between 160 and 180 miles depending on the availability of fuel stations.

Beezageezauk.

Offline Mosin

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Re: MPG
« Reply #3 on: 22.06. 2010 20:34 »
I've just realised that my first post doesn't make much sense - I suppose tht this is what happens when I am thinking one thing and typing something else!

I was actually pondering what a difference I was likely to expect from having sorted out my carburation problems. The figures which I gave were with the carburation well out and the bike sooting up on plug whilst running lean on the other. Having rectified this by fitting a bias gasket and dropping the carb needle by one notch, today I filled up again (having covered exactly 100 miles with the new settings). I was very pleased to see that rather than taking 15 litres of unleaded to carry me 100 miles it now only took just under 10 litres to take me back to having a full tank. This would suggest that I am getting something just under 50 mpg. Still not fantastic, but the bike is still running in and I hope that this will improve as things loosen up.

Simon
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England

Online groily

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Re: MPG
« Reply #4 on: 22.06. 2010 21:05 »
Blimey!
I reckon on getting 75+ mpg (4.54 litre sized gallons) from my B in normal back-road running depending on mood, and never less than 60 from the A, often 70mpg. Not much motorway round here, 'tis true, but lots of up and and down the rev range. I'm used to my AMC twins being unreconstructed petrol junkies (less than 60 mpg from 500cc is pathetic), but I've always found the BSAs a bit better and more economical than most other things of the same size. That's a bog standard late B cruising at 50mph, and a bog standard s/arm Monobloc Flash with one tooth extra on the gearbox sprocket, cruising at 60-65 mph. Bog standard 85/95 Octane Euro-gas. 25 to the christian gallon, even with a heavy hand and a pair of mega-carbs, is ridiculous, and under 50 is thirsty even by the standards of those of us who consume wine in  industrial quantities. But under 50mpg on a 3.8 litre gallon would start to sound a bit better!

Bill

Offline gold33

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Re: MPG
« Reply #5 on: 23.06. 2010 01:01 »
Hi,
Early stages of running in but my first refill would have given better than 210 miles for the tank.
I ran a cup full of two stroke oil in the first tank for top end lubrication (shouldn't effect consumption) and am switching to a commercial upper cylinder lube for this tank.
I recall reading somewhere that they should do around 44mpg so I'm ahead of that already. Mostly hills around here so I am able to work the new motor while being careful not to labour it, so far so good.
Darren
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Re: MPG
« Reply #6 on: 23.06. 2010 13:31 »
You talkin' bout me Groily ? *beer*
Average 55mpg out of the '51 A7, 40mpg out of the cafe, and 12mpg out of the A7SS in race trim running methanol.
Time for another muscat.
Cheers
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Online groily

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Re: MPG
« Reply #7 on: 23.06. 2010 14:30 »
you  must have some wrists on yer muskrat! When I had a hairy car I thought 8mpg from triple webers and 300 bhp wasn't that good . . . looks brilliant now!
But seriously, it's hard to make cooking iron engines like either of my BSAs drink heavily here given the nature of the roads. So we suck straws or chew turnips as we roll, and have to test the brakes before we've really exercised the engine, on twins anyway. As well as watching out for radars nowadays, sadly. Even pushing my point-and-squirt cafe racer Connie quite hard, I still get around 55 to Her Majesty's Proper Imperial Gallon, and the same or better on a much-worse-abused twin-carb over-bored '53 G9 Matchy-based hybrid (now under big-£££-signs repair in the shed after a little, er, technical hiccough that did short term wonders for oil company stocks). 
You have to have either good economy or a big tank here in France on Sundays, as gas can be hard to find . . . . so the BSAs are brilliant on both counts. The B's just a bit slo-o-o-o-w, obviously.
Bill

Offline A10Boy

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Re: MPG
« Reply #8 on: 24.06. 2010 16:23 »
I went to the BSA day at Kettering a few weeks ago. Starting from home with a full tank [topped up from a jerry can cos I mix valvemaster in it], the run to kettering was at a steady average 65mph and around 60 miles on motorways and dual carriageways, [Yes we have Carriageways here].

When I got there I looked in the tank and the level had only dropped by about 2 1/2 inches - I recon thats about 3/4 of a Gallon for the 60 miles, or around 75 - 80 MPG. Thats a real Gallon as used in the British Empire, not one of those new world short changed micky mouse measures.

75 - 80 MPG thats not bad...
Regards

Andy

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Re: MPG
« Reply #9 on: 24.06. 2010 19:48 »
I recall getting what I thought was  around 60mpg two up on my Flash in the sixties, don't seem to be able to get anywhere near that now, perhaps the carb needs to be leaner although plugs don't soot up, I do use a hotter plug than original to cure that, maybe I should have persevered with the tuning a bit longer.
Then there is today's fuel but that surely is designed for modern engines that give better consumption than fifty year old cars

Questions questions
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline alanp

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Re: MPG
« Reply #10 on: 24.06. 2010 20:35 »
 I'm running in my RGS engined A10 at the speed range 60 to 70 mph for approx. 30 to 40 miles at a time and have noticed that I top up the tank with a quantity which approximates to 10 or 11 miles/litre, i.e. at least 45 miles/imperial  gal.
If(?) the tank is 3 imperial gallons/14 litres, this would take mine maybe 140+ miles before I push it.
Clearly a less tuned engine and lower average speeds will give a whole lot better mileage than this.
Alan
Member of the 'Last of the Summer Wine Club - Jennycliff'.

Offline Mosin

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Re: MPG
« Reply #11 on: 04.07. 2010 11:46 »
I've been using this rather nifty on line MPG calculator recently http://www.torquecars.com/tools/uk-mpg-calculator.php

It is revealing that I am consistently still only getting around 42 mpg from my A7ss This is on a rebuilt engine using standard unleaded with a dash of lead replacement additive added. Obviously this isn't great at all, but my plugs appear to be burning absolutely fine and I was wondering where the best place might be to start looking for answers to the high fuel consumption might be....

I have tried riding it absolutely as gently as possible and it doesn't actually seem to affect things very much.
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England

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Re: MPG
« Reply #12 on: 04.07. 2010 12:21 »
Your right wrist. Or your calculator needs new batteries. LOL.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline chaterlea25

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Re: MPG
« Reply #13 on: 04.07. 2010 19:18 »
Hi Simon,
what gearing is your bike running?? and what size tyres??
It may improve things to increase the gearing or fit a larger section rear tyre??
Despite the plugs looking fine the mixture may still be too rich???

My SR has a Mikuni setup and fuel consumption doesnt seem to be an issue??

Jeez!! my Beemer 1150 will give 44/46 mpg

Cheers
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline Mosin

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Re: MPG
« Reply #14 on: 05.07. 2010 15:01 »
I was riding into work this morning doing some thinking in my head....

When I got to work, I checked the trip on my speedo which told me that I had covered 14 miles since leaving home. I have just checked the same route on google maps which gave me a distance of 18 miles (which is also what I get when I clock the route in my car).

This would give a discrepancy of 22% on the bike odometer which wouild suggest that the 100 miles which I thought I was getting to 10.8 litres of unleaded may actually be closer to 122 miles thus giving me an improved MPG of 51 rather than 42. Still not ideal, but definately getting better....
1960 A7 Shooting Star
1959 D3 Bantam
1994 Triumph Trident 900

North West England