BMW K bikes (Bricks)


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desperado

desperado
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Hey guys

1985 K100RT

I've had this issue over the last few hundred miles and have tried various fixes. It feels like I'm running out of gas even with a full tank. I lose any throttle response and the bike becomes jerky. It's doesn't feel mechanical. It feels like a fuel/air/mixture problem. If the bike is cold, it will take 35-40 highway miles to start showing symptoms.

Attempted fixes:

-Fresh air filter
-Fresh fuel filter
-A few rounds of injector cleaner
-New fuel pump (purolator 2042 mod well documented here: http://www.motobrick.com/index.php/topic,2058.25.html)
-Checked electrical going into the tank

I'd love any suggestions. Home is Los Angeles but I'm currently in Yakima, Washigton. I'm going to start checking the fuel rail and injectors and I'll update when I can.

    

Brad-Man

Brad-Man
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Have you tested the gas tank vent?

A vacuum build up can act like this...


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Toys don't make the man - Man makes the toys....
 Intermittent loss of throttle. (Feels like I'm running out of gas) Usa-lo10
    

desperado

desperado
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I've had venting issues in the past and it doesn't seem to be the case now, but yes, very similar symptoms as a venting issue.


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1985 K100RS
Los Angeles, Calif.
    

K75cster

K75cster
Life time member
Life time member
Ignition key too heavy, or kill switch not used much, or the four pronged connector to the tank under the R'H side cover may be corroded, cleaning or fiddling with these would eliminate most reasons for it being electrical


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

92KK 84WW Olaf

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K75cster wrote:Ignition key too heavy, or kill switch not used much, or the four pronged connector to the tank under the R'H side cover may be corroded, cleaning or fiddling with these would eliminate most reasons for it being electrical
Could also be located front left of the fuel tank on early 85? But yes I had this problem. If the connections go poor it can result in arcing inside the connector and running as you described. Easy fix to close up the connectors a little so there is a better connection.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

Holister

Holister
Life time member
Life time member
desperado wrote:
...... I lose any throttle response and the bike becomes jerky. It's doesn't feel mechanical. It feels like a fuel/air/mixture problem. If the bike is cold, it will take 35-40 highway miles to start showing symptoms.
.......
If the problem only happens after the engine has reached operating temperature, and you feel its fuel related, it's probably the temperature sensor.
The testing procedure is described in full on this link about ¾ way down the page....
EFI/Electronic ignition troubleshooting

Easy to do and will rule it out if nothing else.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Intermittent loss of throttle. (Feels like I'm running out of gas) Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

92KK 84WW Olaf

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Thanks KH, I missed the bit about operating temperature. As you correctly say, operating temperature is the key.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 48,061 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 61,190 miles

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Anyone else here suspect a faulty Hall Effect Sensor?


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Rick G

Rick G
admin
admin
With the description that is where i'd be looking.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

desperado

desperado
active member
active member
Thanks for the tips guys. I'm going to check out the Hall effect sensor this morning. We'll see how it goes.


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

desperado

desperado
active member
active member
Ok I'm back. Like I said before, I'm 1100 miles from home and don't have quick access to a heat gun, but I read on another forum to test it with freeze spray. I just went on a 60ish mile ride and stopped three times to spray the hall sensor cover, but the issue kept happening. I tried a hair dryer but I don't think it would have gotten hot enough to make a difference.

I also tried riding with the gas cap open to make sure it isn't a tank venting problem.

I'm not completely sure the Hall Sensor isn't the issue. The freeze spray seems like a vaguely crude way to test so that may still be at play.

I'm going to let the bike cool off a bit and then take the fairing and the tank off so I can start checking things there. I'll check plugs then as well.

Any other suggestions are fully welcome.


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

Avenger GT

Avenger GT
Life time member
Life time member
You're wasting your time spraying the cover with freezer. You should take it off and spray the hall sensors directly.

    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
desperado wrote:but I read on another forum to test it with freeze spray. I just went on a 60ish mile ride and stopped three times to spray the hall sensor cover, but the issue kept happening.

You need to shoot the spray directly onto the hall sensors, not the cover.  When you go out, do it without the belly pan(You have a K75S, correct?) and only two screws holding the cover on so you can get it off quickly.  Carry the allen wrench and spray where you can get to them quickly when you stop.

Run the bike until it barely runs, stop, pull the cover and spray under the "cup" to get as much as you can on the stuff under it.  Try to start the engine and see if it runs better without waiting the normal amount of time needed to cool down.  If the engine runs better as soon as you cool the sensors that will tell you that they are the problem.

The freeze spray is a diagnostic tool, not a fix.  As soon as the sensors heat up again the problem will come back.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

desperado

desperado
active member
active member
Yeah I'm definitely not expecting a fix from it, just trying to track down my issue, fix it, and then get home. Thanks for your help.


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

desperado

desperado
active member
active member
And it's actually an 85 K100RT


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Oops... Senior moment.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Holister

Holister
Life time member
Life time member
I think if it was the HES you'd lose ignition and the engine would just die. They work or the don't.
My money is on the temperature sensor (re my post #6). Pull the FICU plug and measure the resistance between pin #10 (sensor) and pin #13 (earth). You should get a reading of 2.5 kilohm at 20oc and 300 ohms at 80oc. Don't worry too much about the temp of the engine... just cold and hot.
Count the pins from the lead end of the plug including the blanks.
It's a very quick and easy test that takes just 1 minute, even if just to rule it out before you go to the trouble of playing with the HES.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Intermittent loss of throttle. (Feels like I'm running out of gas) Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

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