milage and tanks

[45disco]

what kinda millage have folks been getting on the r80 g/s. i am trying to figure it out, i have an r100gs tank gallons (lt) ? i am getting consistantly 32 mpg ish. because of this i am looking for a bigger tank 43lt or pd. any help.


cheers,
jim

 

[bmwrich58]

Over the years owning 4 Airhead GS's they all averaged about 38 mpg's.
That's USA measures.

 

[Rob Farmer]

High 30's to low 40's for me. If I keep the speed down to 60 Mph I can get it into the 50's.

First post? Welcome aboard

 

[Bickers2208]

I can get 55-60mpg on a motorway run sitting between 4500 and 5000rpm... Uk measures, that usually equates to 190-220miles before reserve, and only ever done 23miles on reserve with no problems.

 

[Voyager]

My R100GS tank holds 26 litres.

I get 10 miles per litre / 46mpg unless I am trying to keep up with outside lane motorway traffic in a headwind, when it can get down to 40 mpg. Not having a screen can be a pain under those conditions.

The bike has twin plugs which may improve the consumption.

Bob.

 

[45disco]

mine , i think, just doesn't get the mileage. the most i have ever seen is 32 most of the time its in the 20's,(more when i carry heavy loads), when i got the bike the needles were set high for altitude, i changed back to stock setting and syncroed the carbs, valves are great(motor was freshed up about 6k ago) exhaust is a bit sooty but plugs are not. the bike runs great, has power from 1800 low end to2800 then climbs fast to 7k rpms. my rpms are about 4k at 60 mph. most of the mountain driving is in the 55mph range with no load. i weigh 200lb. 6'4" tall

so i am sure if i have overlooked something or not. because trip weight and 25-28 mpg is not good enough especially when my discovery get close to that.

jim

 

[bmwrich58]

mine , i think, just doesn't get the mileage. the most i have ever seen is 32 most of the time its in the 20's,(more when i carry heavy loads), when i got the bike the needles were set high for altitude, i changed back to stock setting and syncroed the carbs, valves are great(motor was freshed up about 6k ago) exhaust is a bit sooty but plugs are not. the bike runs great, has power from 1800 low end to2800 then climbs fast to 7k rpms. my rpms are about 4k at 60 mph. most of the mountain driving is in the 55mph range with no load. i weigh 200lb. 6'4" tall

so i am sure if i have overlooked something or not. because trip weight and 25-28 mpg is not good enough especially when my discovery get close to that.

jim

Sooty exhaust...hmmmm maybe running rich.
What's the plugs look like. From the Factory,these bikes are jetted lean,at least here in the States,EPA an all

Plugs will have a titch of whiteness,lean conditions with the stock/factory jetting. Proper plugs should have a tan color (brownish) any black is usually running rich.

Airhead's especially being carburated can and are touchy.
So,check your jetting (slow and main jets),the needle *clip* adjustment from the top,and worn needles will also effect gas mileage,along with proper carb adjustments and balance.
Vaccum leaks around the "black boots" to cylinder heads,even tops of carb's are known to suck vaccum.

Believe it or not,Float height can make an engine run rich or lean.

So,your hands are full,but check all those items.

Bing International here in the States sells a great Carb Book.
Or search around online for diagrams and the like.
Goodluck !

 

[Sean Kelly]

Hiya

Gunk from the breather into the airbox can work its way into the carbs and build up around the main jet which does bad things for fuel consumption.

Sean

 

[Beemerboff]

I get over 20 km / litre or 56 MPG from the R100GS and around 17 Km/litre or 48 mpg from the 900 cc R75/7.

The R75 probably needs a tune as I've gone 440 km on a tankfull.
They both have oversize rear tyres, a 120 on the R75 and a 140 on the GS so I am probably going a bit further than the reading.

The usable capacity of the tank depends on the height of the standpipes in the top of the petcocks, and the amount of gunge on the gauze tube round them - I have difficulty getting any more than 22 1/2 litres out of the GS tank while I can get 24 1/2 out of the supposedly smaller R75/7 tank, yet some people report getting 25 1/2 litres into the GS's tank at fuel stops.

However , consumption isn't always thus as a good portion of pumps in Oz read about 10% over , always the same brands and always while they are discounting------.

 

[(RIP) pastyman]

On the way back from Basketville Ball, I was getting a steady 45 mpg with some motorway (70/75 mph) and some cross country A and B roads taken at a fair pace. 19 ltre tank so 160ish before reserve.. Not tested that yet.

Yours should do more than 30 though.
You have tried lifting the little peddle thingy by your left foot hav'nt you

 

[Deleted Member MS]

Just done experiment on mine (93 Gs100).

Did exactly 45 to one gallon of unleaded, at 70mph, on motorway.

Did 40 miles on motorway on the reserve tank, at 70 mph,but only 29 around town on reserve.



Ps . .does that mean to get better fuel consumption around town, do 70mph everywhere !!!!????

 

[45disco]

i did away with my pre-muffler any put in a y-pipe and opened the airbox up. took flutes off to make inlet holes bigger as i have a uni high flow filter (can clean on long dusty trips). the bike sounds better above 3500 rpms, has that twin rumble. it pulls harder, so i have pick up some hp, it seems. i also don't have to throttle it as much above 60 mph, so i'll test the mileage after this tank of fuel. i have been getting 175 miles to 5.4 gallons then hitting first reserve. i get about 30 miles on first reserve and ? on second(i still have a fair amount of fuel at the bottom though)

cheers
jim

 

[45disco]

up date

sorry it has been awhile, mates, the timing was way off, PO, or shop in washington st. set the timing retarded fully adv @2200 rpms resulting in low fuel millage at speed, just did a trip and got 40 ish with twin 40l panners full.

jim

 

[Sylvester]

Always in the low to mid 40's. Piss poor really as I ride like Miss Marple.

 

[Sylvester]

Oh, by the way what speed do you have indicated at 5000rpm? Not sure what G/box or final drive is fitted to mine.

 

[45disco]

i was told that around 5k rpm is around 70mph. i know 4k is about 62mph. i think 5k rpms is around 75mph(78). cause doing the math if it is only 70 than the g/s only can go 90mph and i have heard of guys doing 110mph on the autobahn. bmw clames that the g/s 's top continuous speed is 110 mph@7000 rpms. that is 1mph every 63.63 rpms... that times 70mph= 4454 rpms,, 80mph would be 5090rpms. but that is not include idling. assume your idle is 1000 rpms then the ratio is (54.54x(mph))+1000= mechanical speed so 54.54x70=3818+1000=4818.. 75mph@5090, 85mph@5636. the info i have came out of the original bmw r80g/s owners manual. i personally this the ratio is between 54.54-63.63 b/c when in first gear at 1000rpms i am moving at about 3 mph

hope this helps
jim

 

[Voyager]

Oh, by the way what speed do you have indicated at 5000rpm? Not sure what G/box or final drive is fitted to mine.

I was out on mine the other day and did a quick burst to check . . .


5,000 rpm = an indicated 84 mph (new speedo).

That's on an '89 R100GS.

I believe BMW claim a top speed of 115 mph for it (or, 4mph slower than the R1150 GSA ).

Bob.

 

[45disco]

i looked again at the owners manual, they(bmw) implies that 70mph@4500. all g/s should have a 37/11 rear ratio. you can get a higher ratio but it is expensive and just about impossible to fine,, like a 33/11,32/10. i do believe that the r100gs has a 33/11(or something close) which will lower rpms by about 400 rpms which is why your bike reads 84@5000 instead of 84@5400-5500 on the g/s. that is my guess.

jim

 

[Sylvester]

Thanks for the info, mine is pulling through the redline in top with ease.

 

[Sylvester]

Did the 5000 rpm this morning, reading 120 kph. Bevel box has 34/11 on it. I would love to drop the revs by 500 rpm, it would make the autobahn much nicer. Any ideas?