BMW K bikes (Bricks)

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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

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Have you tested the gas tank vent?

A vacuum build up can act like this...


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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

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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


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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.


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1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

Holister

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@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.


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1988 K100RT     VIN No.  0094680
1989 K100RT     VIN No.  0097367 (naked)  
1996 K1100RS   VIN No.  0451808
     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.


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1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

Point-Seven-five

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Anyone else here suspect a faulty Hall Effect Sensor?


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Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

RicK G

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


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"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats."  from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

desperado

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


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1985 K100RS
Los Angeles, Calif.
    

desperado

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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.


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1985 K100RS
Los Angeles, Calif.
    

Avenger GT

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

    

Point-Seven-five

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@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:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

desperado

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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.


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1985 K100RS
Los Angeles, Calif.
    

desperado

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And it's actually an 85 K100RT


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1985 K100RS
Los Angeles, Calif.
    

Point-Seven-five

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Oops... Senior moment.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Holister

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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.


__________________________________________________
1988 K100RT     VIN No.  0094680
1989 K100RT     VIN No.  0097367 (naked)  
1996 K1100RS   VIN No.  0451808
     Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

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