Author Topic: What? Out of petrol? Consumption concern.  (Read 2478 times)

Online RichardL

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Re: What? Out of petrol? Consumption concern.
« Reply #15 on: 12.05. 2015 15:11 »
60 MPG! OMG, I'm not even close. I know I'm running rich but that's double. Mike, I think you must be fit and thin (unlike myself), leading, in part, to that exceptional mileage. Then, there is the question of compression ratio. Correct me if wrong, but I think my 9:1 pistons may lead to more consumption than, say, 7.25:1. Then, there is the question of where you ride and when you take the measurement. Was it just after a 60-mile run on open highway? My riding includes a lot of suburban traffic just to get to someplace open and pleasant to ride, and that is still not open highway. Of course, if you like to lay on the throttle, as I do in acceleration (not really excessive speed) I'm sure that's part of the problem. OK, sorry to be boring, but all of this, and other things, don't seem to explain such a disparity in our respective mileages, or do they?

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline Topdad

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Re: What? Out of petrol? Consumption concern.
« Reply #16 on: 12.05. 2015 15:38 »
Richard ,I'm on" b" roads mostly ,fair share of cars and even tractors so very few hold ups usually do about 60 miles on a round trip which also has some dual carriageways ,about 10 miles in total . Don't rev the backside but keep up with the traffic and on the last bit stay infront of  most of the cars .Seem to be getting approx 60 to a gallon if not more. used to average about 30 on an outfit when the pure thing was flogged  mercilessly , Cheers Bob.
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Online cyclobutch

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Re: What? Out of petrol? Consumption concern.
« Reply #17 on: 12.05. 2015 15:40 »
I don't get 60 out of mine I don't think, maybe nearly 50? Richard, don't forget where you are the galleons are smaller.

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Online RichardL

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Re: What? Out of petrol? Consumption concern.
« Reply #18 on: 12.05. 2015 15:46 »
I don't get 60 out of mine I don't think, maybe nearly 50? Richard, don't forget where you are the galleons are smaller.

I'd forgotten about that completely. That makes me feel 20% better.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline Dynamo Regulators Mike

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Re: What? Out of petrol? Consumption concern.
« Reply #19 on: 12.05. 2015 16:02 »
Yes 60 mpg (imperial gallons that is, US ones are 20% less of course) is probably the low side of average for mine. Mine is not running rich (and the oil stays clean longer). I do not pussy foot about but do ride smoothly I would say, use 'throttle sense' to save sharp braking but not unusually slow. In fact some other BSA'ers on our club runs reckon I ride too fast for them. Typical cruise speed on main roads is 65 mph. This consumption ties in pretty well with contemporary road tests, and many others' findings.
Mine is about 8:1 with Alloy head, in fact higher compression means better efficiency, and could give better figures than lower ratio, if not used to full performance potential. Mk1 28 mm concentric fitted. I guess ignition settings come into it as well. Mine has Boyer electronic, so at least both sides same timing and decent sparks (as it should with a good mag), and timing set by feel not book figure which is a guide. Cheapest fuel goes in 95 grade. No issues.
Definitely not thin at 14 st plus, (nor particularly fit for that matter), and often ride two up with better half on rear.
As a comparison I see about the same 60+ mpg with my ER6 Kwacker with about twice the power. Just over 50 for the 90 hp Tiger 800, and about 50 mpg for the Skoda Fabia 1200 car.
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Online RichardL

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Re: What? Out of petrol? Consumption concern.
« Reply #20 on: 12.05. 2015 18:52 »
Definitely not thin at 14 st plus, (nor particularly fit for that matter

Well, there's another 8%, so, I'm down to a 43.5 MPG comparison. At least now I can TRY to shoot for similar results.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Online Greybeard

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Re: What? Out of petrol? Consumption concern.
« Reply #21 on: 13.05. 2015 10:30 »
...Richard, don't forget where you are the galleons are smaller.
And the pirates are tiny!

Offline Triton Thrasher

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Re: What? Out of petrol? Consumption concern.
« Reply #22 on: 13.05. 2015 18:18 »
...Richard, don't forget where you are the galleons are smaller.
And the pirates are tiny!

They went 3,000 miles on one galleon.

Online RichardL

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Re: What? Out of petrol? Consumption concern.
« Reply #23 on: 13.05. 2015 18:43 »
...Richard, don't forget where you are the galleons are smaller.
And the pirates are tiny!

They went 3,000 miles on one galleon.

Clearly, they were full of wind when they reported that.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline CrispinA10

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Re: What? Out of petrol? Consumption concern.
« Reply #24 on: 13.05. 2015 20:25 »
Well I am still fit and thin - I could outrun a Bantam on a 10k road race  - and I'm only getting 30mpg or less while running in with a very gentle throttle. So there's something wrong. Must be running rich. First step, I reckon, is to try one of these Amal stay-up floats and get the float height right as recommended. The air screw I wound right in and wound out one and a half turns as suggested by Brian Gold Star from Herne Bay to give a starting point, Of course I won't know the effect of that until I use a tank of petrol and find out MPG.
Without wishing to start a new thread, I have been using high octane four star - I assumed that with a higher compression engine that would be wise. Is that utter tosh?

Offline Triton Thrasher

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Re: What? Out of petrol? Consumption concern.
« Reply #25 on: 13.05. 2015 20:34 »
Keep it simple. At gentle speed, you're on the needle jet, which wears- renew it. Also influenced by the cutaway- try bigger.

Online morris

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Re: What? Out of petrol? Consumption concern.
« Reply #26 on: 13.05. 2015 21:37 »
...Richard, don't forget where you are the galleons are smaller.
And the pirates are tiny!
They went 3,000 miles on one galleon.
Clearly, they were full of wind when they reported that.

Please guys, next time give us non English speaking members a little explicative footnote. I had to go over it about 20 times before I got the pun. But when I finally got it.....ROFL *lol* *lol* *lol* *good3*

BTW I get 43,5 mpg (UK gallons that is) out of the SA. Don't have any figures on the plunger because not finished yet (soon to be though *grins*)

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Offline East_Coast_BSA

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Re: What? Out of petrol? Consumption concern.
« Reply #27 on: 13.05. 2015 22:45 »
I think jetting might be part of it, but I'm guessing not the big part.  If you are burning twice the fuel as everyone else, that bike would be jetted so rich it wouldn't run.  There seems to be an efficiency issue going on as well.  Is your cam timing correct, ignition timing retarded, air filter clean, etc.  Also never run more octane than you require.  I'm not familiar with four-star high octane (living in the States).  I'm running 93 unleaded here and my bike runs fine.  You need just enough octane to preventing pre-ignition, any higher octane will produce less power and is less efficient.  This page should give you a good idea of what you are supposed to have for jetting.   

http://www.classic-bike-shop.com/bsa-160-c.asp

Offline CrispinA10

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Re: What? Out of petrol? Consumption concern.
« Reply #28 on: 14.05. 2015 16:38 »
Thanks for suggestions.
The needle is I believe new as the concentric was fitted by previous owner at rebuild and it's only done 200 miles so far. I had a look and it appears pristine. There is no air filter. I agree that if the problem was simply a rich mixture, it would be running terribly and in fact it is running perfectly, with lovely tick over, smooth acceleration and nicely coloured pipes. There is definitely no petrol leak (left a sheet of brown paper beneath it for a week and not a trace).
Afraid I know nothing yet of cam timing - but again, surely that would lead to rough running.
Don't get a chance to look at bike until weekends because of work, but I'm planning on draining the tank and having a look at the petrol cocks - perhaps they are both two inches off the base of tank and |I haven't actually got a problem at all!
Unlikely, but fingers crossed!

Offline duTch

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Re: What? Out of petrol? Consumption concern.
« Reply #29 on: 14.05. 2015 21:23 »

 Doesn't matter how much is left in the bottom when you refill and compare that  to the mileage since last refill...
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