K11 Owners Group

CheapJapCopy · Posted: Sat Jan 10, 2009 11:09 am Post subject: Stupidly low MPG

Hi guys and gals. I know I've been one to bitch about my BM in the past, but she's been really good to me lately..

The problem is, that MPG has been dropping. I had the air filter and battery replaced recently, and after that it lurched down to 25MPG. I have plenty of black soot forming on the exhaust, so it's definitely running rich, but no black smoke, just the usual puff of oil smoke every now and then that some of our machines are wont to make.

I took it to my back-street mechanic and he had a fiddle with it (Replacing a potentiometer), apparently reducing CO2 levels from 7%(!) to 2.5%. This made a small difference, but it's still terrible. I get 160 to a tank when motorway riding, but when I use it in cold weather for a succession of ten mile journeys, I get 100 miles. You can smell that it's running super-rich, especially when cold, and even when warm.

After doing a bit of research, I decided to basically use the mechanic to fit what I thought was causing the problem, which I believe to be the water temperature sensor, next week. I'm also toying with the idea of a valve job, but with 60k on the clock, I wonder whether the valves could be that bad?

Anyway, thanks for any replies.
_________________
1992 K1100RS - Red and gold.

Off the grid · Posted: Sat Jan 10, 2009 1:38 pm Post subject:

Check O2 sensor as well.

35mpg is low-normal.

I usually get 150-60 out of a tank.

25mpg is something wrong though.
_________________
Bane of your existence since July 2006
2007 Triumph Tiger ABS. "Sabertooth"
2009 Husqvarna TE610. "The dirty Italian mistress"

Scott_Anderson · Posted: Sat Jan 10, 2009 3:49 pm Post subject:

Not sure how the UK blends their fuels, but here in the states, anyway, we will loose MPG's with the winter blend fuels.
I'm not an engineer to precisely know what they change, but my mileage most surely suffers in the winter. Both on the bike and in the vehicles.
_________________
Ride safe.

1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

duckbubbles · Posted: Sat Jan 10, 2009 6:32 pm Post subject:

I had the water temp sensor go bad on mine a few years ago. It was spitting gas out the muffler. It was telling the computer that the engine was ice cold all the time.

Frank
_________________
85 K100/1100RS, 321,000 miles, 25 years
96 Ducati 900SS/SP, sold it
05 R1200ST, 35,000 miles, 5 years
400,000 BMW miles

mike toon · Posted: Sat Jan 10, 2009 8:11 pm Post subject: Re: Stupidly low MPG

CheapJapCopy · Posted: Sun Jan 11, 2009 7:10 am Post subject:

Thanks - yes, the battery change could be the culprit. I think I'm going to try and press for fault-code readings when I go to the workshop. From the manual, apparently there's a code "1111" that produces more or less what I'm getting, which is an emergency setting to get you home. The water temp sensor is another likely culprit though, so I'm going to replace that anyway.

I'll keep you posted on how I get on, again, thanks for the replies.

Neil
_________________
1992 K1100RS - Red and gold.

Jim · Posted: Sun Jan 11, 2009 11:17 am Post subject:

I'm sure I'm not the only one here who has had the battery out of the bike numerous times without the computer ever going into limp home mode. I don't think it was the battery...

That said, since you are starting to suspect various electrical parts - I say make sure the connections to those parts are clean. There are various electrical cleaning sprays on the market, as well as protectant compounds - for all those electrical connections that tend to fail.
_________________
Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

Tim (Midland Section) · Posted: Sun Jan 11, 2009 6:56 pm Post subject:

bmwmick · Posted: Mon Jan 12, 2009 10:54 am Post subject:

Shoganai · Posted: Mon Jan 12, 2009 11:24 pm Post subject:

Shoganai · Posted: Tue Jan 13, 2009 12:09 am Post subject:

I suggest the following:

1. Check the resistance of the spark plug wires.
2. Replace the spark plugs.
3. Look for cracks in the exhaust header (will throw the O2 sensor)
4. Look for cracks intake manifold.
5. Look for electrical shorts (major hard to track down Shocked

)
6. Consider replacing the fuel pump and air filter.
7. Consider having a level 2 service done at your shop.
8. Look/smell for fuel leaks.
_________________
1993 K1100RS aka The Shop Whore
1994 K1100RS aka Blue Streak

The long road is a rainbow and the pot of gold lies there.
So slip the chain and I'm off again,
You'll find me everywhere. I'm a Rover. - JT

Nana korobi ya oki

Off the grid · Posted: Tue Jan 13, 2009 3:28 am Post subject:

Shoganai · Posted: Tue Jan 13, 2009 3:34 am Post subject:

gpzoduibh · Posted: Tue Jan 13, 2009 8:04 am Post subject:

I think the temperature sensor in the airbox will also affect consumption and their is a test in one of the stickies that will show you how to compare the two sensors with a cold engine to prove if they are good or bad.
Regards
Bill

found link : http://www.geocities.com/fwarner_au/mc_things/K_fuel_injection.html
_________________
1995 Grinnall Scorpion III(1990 K100 16v motor)
2010 KTM 450 EXC
Moto Guzzi V50 powered hovercraft !
1989 K100RS (8V) special edition
1974 Yamaha DT360
1972 Sanglas 400 T
1980 Yamaha XS110-Watsonian Palma sidecar
1966 Bridgestone 175 dualtwin
1980 BMW R100RS
1979 Bultaco sherpa T 350
1979 Yamaha DT175MX
1990 Honda XR250R

Rafal · Posted: Tue Jan 13, 2009 9:16 am Post subject:

mnb · Posted: Tue Jan 13, 2009 11:55 am Post subject:

replace the fuel filter.

If that doesn't help, check the fuel pump. There could be a multitude of other causes, but those are the first two I'd check given what you've already done.
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M N B
1997 BMW K1100LT ABS Special Edition
2003 Husqvarna TE610e
2007 Harley Davidson Road King
2009 BMW F800GS
2011 Husqvarna TE310
2014 Ducati Multistrada Pikes Peak MNB Edition

CheapJapCopy · Posted: Wed Jan 14, 2009 7:11 am Post subject:

Well thanks for the wealth of advice (Apart from Shog's most unhelpful comment about her fuel consumption Wink

).

She's in the shop today being pored over and investigated. Fingers crossed that my mechanic will find the cause, if not then I'll have to get a multimeter and start prodding.
_________________
1992 K1100RS - Red and gold.

Milton · Posted: Wed Jan 14, 2009 5:19 pm Post subject:

I would check the throttle position sensor. Easy enough to check with a good multimeter.

Milton S.
_________________
Jethro Tull: Thick as a Brick!

1992 K100RS 48K. Dead for now.
1998 Triumph Tiger 43K->56K. Doin it in the dirt.
1978 Honda CB400T 32.5K. For my boys.

AndrewD · Posted: Wed Jan 28, 2009 7:38 pm Post subject:

You should pop over and see about balancing the fuel bodies/setting TPS. Come and say hello on redsoket we meet up pretty regularly.
_________________
AndrewD

1994 K1100RS in Black
www.Gabfesterst.com for all BMW riders

Technician · Posted: Fri Jan 30, 2009 2:43 pm Post subject:

A friend of mine had similar heavy fuel consumption and when we got to the bottom of it turned out to be the fuel pressure regulator at fault.
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Fat Ba***d with a K1100LTse
Squire D18 trailer
Garmin Zumo 660
"Run it round the block to see if the wheels fall off!!!!"