The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: bangpaul on July 21, 2011, 03:38:53 AM
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I've worked out that my bike is doing about 14 kms to a litre. I know these bikes are far from efficient, but that still seems a bit rich. Is this normal? How can I improve efficiency?
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My 79 is doing exactly the same. It's not ideal.
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That's roughly 40 mpg (UK) which doesn't seem very good to me unless you are flat out all the time.
I average 64 MPG overall and have been regularly hitting a best of 70 mpg this summer and although I have a smaller engine there is almost no difference R45 vs R65 in the official fuel consumption figures.
Besides the usual issues of correct float levels and unworn needles and jets, my secret for good fuel consumption is to tune the idle mixture screws properly with a hot engine. That means turn them in till it stumbles and out again only enough for smooth running which is likely a screwdriver width - none of this "and another 1/4 turn out" nonsense that you may read about. Although I've never read it I believe the Bing manual advocates a trial and error method of ride and adjust leaner to achieve the best possible idle mixture. The idle mixture setting has a much bigger impact on overall fuel consumption than most people imagine. This is because the majority of the time we only use 1/8 to 1/4 throttle where the idle circuits still have a big influence. This has worked for me to achieve 60+ MPG on every bike I've had in the last 40 years with one exception and that was a Z900 which had no earthly hope of getting near that figure.
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The final drive ratio is a main cause for the not so great fuel consumption .
The 1000cc bikes of the same era get about the same or a little better than the R65 .
You can try different jets and what not, but it won't result in much better fuel consumption, I've tried it .
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I flog the Dawg pretty hard and get right around 40 miles per US gal.
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Thanks Barry, interesting advice!
I'd imagine with fuel consumption like that you ride conservatively? And you haven't geared the bike taller?
That's one thing I've heard - the R65 can handle 3.20 gearing just fine.
My beemers tend to get anywhere from 40 - 50 mpg, but I'll have to try your trick and see what happens.
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I don't know if you noticed his signiture, Barry has an R45, not an R65 .
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I'd imagine with fuel consumption like that you ride conservatively? And you haven't geared the bike taller?
My figures are UK gallons so they will be approx. 20% higher than US gallons. Also in the UK we have only 5% of the evil ethanol in our fuel so far which may make a few % difference.
I get 70 MPG riding quiet country lanes at typical 50 - 55 MPH maybe occasional 60 MPH so that means I'm not exceeding 4500 RPM.
I don't often ride or enjoy 70 MPH type highways but even then I get 60- 65 MPG.
My R45 is not geared taller in fact quite the opposite I'm revving more than any R65. The carbs are 28mm so maybe a bit more efficient than the 32's at small throttle openings. Although the BMW official consumption figures in the riders handbook are very little different R45 to R65 I think that's based on 62 MPH. I probably do better than an R65 at lower speeds. .
60 MPG should be easily in reach of an R65. I'm sure Lou got that figure recently.
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Thanks for that Barry - makes for a better base to compare.
My last fill up (today) took 4.4 gallons (though I did fill it higher than usual - normally I fill to the bottom of the filler neck, this time to the hole half way up) and I went 215 miles for 49mpg.
My bike's far from stock though - with the CC products 850 kit, head work, 34mm flat slide Mikunis, and a taller 3.36 final drive. This is a combination of highway and backroads riding. On the highway (in town) it's 55 to 65 and 35 to 45 in town.
So let's see - to convert to UK mileage I'd need to multiply that by 20% which gives about 60, and then there's the alcohol to factor in as well. I guess I'm not too far behind you.
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I calculate consumption measured from reserve to reserve which I think should be fairly accurate and repeatable. I note the mileage when the bike goes on reserve and typically add 15 litres. I have a record of all fuel used. There is a very obvious winter summer cycle due to cold starts and short commutes in the winter and it's interesting to see how average consumption has improved from roughly 60 to 65 MPG over the last 4 years as I have gradually dialed in the carbs. Looking at the poor result in 2007 I can cross check with my service records and the big improvement the following year resulted from cleaning out a clogged emulsion tube on the LH carb.
(http://)
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Interesting stuff Barry,
I am sure that Lucky Lou said recently he was getting circa 60mpg. I shall be checking mine as I build the history of the bike once it is back on the road.
Chris
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I have not actually scientifically checked mine, but I have a feeling its pretty bad, I'm sure my carbs could be tuned better, but as the bike runs and feels well, I'm loath to go messing.
Probably come winter I will do a carb rebuilds and work on a good tune after that.
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Last time I checked mine I got 64 mpg on an Imperial Gallon. That would equate to approximately 43 mpg in US gallons.
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According to the BMW brochure of 1981, the fuel consumption of the 65 is 61.4 imp gal.
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Roughly 45 MPG '83 mix riding. I've done nothing to the metering.
[size=8]1983 R65 Monmouth County, NJ[/size]
(https://lh3.googleusercontent.com/-19EoQJVDXQU/Th0Npco4RaI/AAAAAAAACxA/mISOpMdkhKs/s640/100_1489.JPG)
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Last time I checked mine I got 64 mpg on an Imperial Gallon.That would equate to approximately 43 mpg in US gallons.
I think you might have meant 53 mpg in US gallons.
This is an accurate conversion table based on 1 US gal = 0.83267384 Imp gal.
You can convert US/mpg to Imp/mpg by adding 20% and it will be close enough.(http://)
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... I've done nothing to the metering.
...and from the looks of that photo, nothing's getting done around your house and yard either. [smiley=ROTFLMAO.gif]
Air4, you might want to park your R65 for a couple hours and put a few miles on the riding lawnmower before SWWBO serves you with "papers". [smiley=whip.gif] I'm just saying...
Monte
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Thank you for looking beyond the R65 porn MONTMIL and seeing the big picture. ;D
That was part of my first big road trip on her (500 miles r.trip). The last 50 miles of that trip felt like I was riding a tractor in downtown Manhattan,N.Y. ... Phew, I was glad to be off the G.S.P. and far away from the other returning Sunday drivers.
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On my last fill-up, just over 48mpg. Naked bike, no bags. Long ride up the coast, mountain roads, 50 to 60 mph, brief stop and go, short drive on freeway. In city traffic, 40mpg.
Steve
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Last time I checked mine I got 64 mpg on an Imperial Gallon. That would equate to approximately 43 mpg in US gallons.
An Imperial gallon equates to 1.2 American gallons. Dividing your figure of 64 by 1.2 gives me 54mpg, not 43.
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Alcohol content of the fuel can make a real difference in fuel consumption .
I've had my '81 R65 since January '81, I've gotten to know it quite well .
Before ethanol was added to the fuel and with a 55 mph national speed limit, I could consistently get upper 40's mpg .
Now with 10% ethanol, I have lost about 5 mpg .
Also the speed limit on limited access highways, we call them Interstate highways here in the US, here in Aridzona is 75 mph, that will further reduce your mileage about 10-15% over 55 mph .
Keeping an indicated 80 mph on my R65 (actual speed is about 77-78 mph) 36-38 mpg is more the norm now .
I could easily go 225-230 miles to reserve 10 years ago, now it's more like 195-200 miles to reserve .
From the looks of it 15% ethanol fuel is coming in the not to distant future here in the US .
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Wow. Fully comprehensive response as I've come to expect.
Barry, I'll definitely give your method a go as soon as I raise the courage to attempt my first carby tune.
I never knew there was a difference between US and imperial gallons. How incredibly ridiculous. Metric for world peace, I say. (How long is an American mile?)
I took the old girl on it's first long run this past weekend. Managed to get 16km out of the litre at an average of 110km per hour, rather than the 14 I get around town. I do tend to wring it's neck a bit. After 4 thousand revs is where the fun seems to begin.
Well, here's to the wealth of shared knowledge. Thanks all.
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I get right at 200miles to a tank so right at 40. But I run the crap out of this bike. I keep everything in tolerance and ride at 65-70 MPH. If Im on the freeway (which is rarely) I have the bike at 75-80+. I have done the ton once or twice on it now. I shift at 4500-5000 and I ride this bike like I feel it was meant to be ridden. [smiley=bmw_smiley.gif]
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My trip to the BMWMOA rally - total of just over 1100 miles ridden over a span of 4 days, mostly (~75%) secondary roads @ 55 MPH with a couple hundred miles of interstate at 70-75 with BIG hills and high temps, netted an average of 45 MPG (US) for the whole thing. Lowest daily fuel mileage was just over 42 MPG.
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My ride back from Bloomsburg LRB got 61 mpg imp. so I was ever so pleased as he is telling me he is in pretty good order. I trundled along at 65 mph mostly on the empty 4 laners and 55 on the secondary roads. I just didn't feel in a hurry and was happy I was alone and not having someone to keep up with. I usually fill up in the neighbourhood of 180 miles. I have never gone on reserve as a rule. Need to stop before that!!
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Around 10 miles per litre - R80/7, R100RT, R45, R65 - all about the same
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... How long is an American mile?
One US mile (5280 feet) equals 1.609 kilometers.
As to my R65's fuel mileage, I have never actually done the math to get an exact figure for either one of the bikes. I just wait until they go onto reserve, then fill up again. Ride on.
Monte