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Thread: 1992 K100RS Any advice?

  1. #1
    Kbiker BCKRider's Avatar
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    1992 K100RS Any advice?

    (Sorry about the long story - may help you diagnose the problem and solution.)

    Last Sunday left on a 330 mile trip to fish with a friend, bike running great. Stopped for gas and after filling up, noticed there was a tanker truck parked on the premises. (Yes, I have heard you should go to the next station when you see that, and no, I wasn't paying attention.) Go over a hundred miles, bike still running perfectly, and am within 50 miles of my destination when the bike suddenly won't accelerate.

    There is maybe a five minute period where I can maintain 60 mph but without the usual acceleration when I roll on the throttle. Then suddenly all the power is back. Then there are a few "power cuts" of a second or so and immediate restitution of normal power. Then another several minute cut of power with another restitution of power which lasted until I got to my friend's place. I'm thinking "bad gas" and the next day bought a can of Sea Foam, added half of it to the near empty tank, filled up the tank and took the bike for a 20 mile ride. Great power; no problems. Parked the bike in friends garage for a few days while we fished. (Not relevant, but yesterday caught three trout over 3 pounds - kept one - on the most improbable #14 dry fly fished deep on a sinking line!)

    The first 120 miles of my trip home today were absolutely free of any bike problems. Then the loss of power returned, and stayed. Adding the rest of the Sea Foam and filling the tank didn't help. So I had something like 200 miles of rainy mountain pass riding on a bike that had something like a third of its 100 hp - always wondering if it was going to simply quit. Gear kept me warm and dry, but it was a scary trip. Did make it home.

    A guy working at our place (former bike owner and one who had recently done some work on his old Volvo and failed to install one spark plug wire) suggested it sounded like the bike was running on three of its four cyclinders.

    So, what say you about the plausible causes of the problems (and also the chance I've done terrible damage to the engine?) I'm thinking the most probable cause of the intermittent problems was not water in the gas but small grit which passed through the fuel injectors and, finally, a piece which blocked a single injector. But I know next to nothing about engines.

    I clearly will have to take this bike to a mechanic - and it does still run, barely. Your advice would be most helpful if there are other possibilities which fit the symptoms described but have nothing to do with water or particles in the gas. That COULD have simply been a coincidence.

    Thanks in advance for your thoughts.
    Doug
    1992 K100RS

  2. #2
    3 Red Bricks
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    Pull the fuel filter. Pour out the gas in the filter, then let the filter dry out for a couple of hours.

    Then lightly blow through the filter in the direction of the arrow. If you feel ANY resistance, it's time to change the filter. If you feel real resistance, it's probably the major part or all of your problem. Change the filter and see how it runs.


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  3. #3
    Brick Pilot der ziegelstein's Avatar
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    What Lee said.

    I experienced the exact symptoms on my way home from work last month. I replaced the fuel filter, all is well.
    Jim McGill
    '87 K100RS
    '04 R1150RT

  4. #4
    Registered User Overkill's Avatar
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    If you are not comfortable pulling the fuel filter yourself you might drain the gas and see if there is water in it. If you put it in a clear glass container it will be VERY obvious. The water will be on the bottom (after a few minutes to settle) and there will be a very clear line where the water ends and the gas starts. If there is no line then there is no water. But even if it is water and not debris that you picked up then you should probably replace the fuel filer anyway. So I'm not sure if I helped at all!
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    Kbiker BCKRider's Avatar
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    changing the fuel filter didn't work

    The problem is back to the "intermittent" stage - full power maybe 20% of the time, lacking power 80% of the time.

    Three other clues I forgot to mention in the OP: 1. the bike used almost twice as much fuel as normal while running badly, 2. the idle is slower than normal and the engine just sounds rough when it lacks normal power and 3. the change from full power to little power and vice versa is instantaneous - it is just as suddenly running well as running badly.

    Any thoughts on what to check next?
    Doug
    1992 K100RS

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    Registered User WalterK75's Avatar
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    I had a loss of power on a 1991 K75 which turned out to be the heat sensor in the engine. I don't know if this could be your problem.
    Walter

    G. K. Chesterton wrote - "The traveller sees what he sees, the tourist sees what he came to see."

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    Registered User argent brick's Avatar
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    Quote Originally Posted by WalterK75 View Post
    I had a loss of power on a 1991 K75 which turned out to be the heat sensor in the engine. I don't know if this could be your problem.
    By "heat sensor", do you mean the one that checks coolant temp. and sends info to the fuel injection?
    Lynn
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  8. #8
    Rally Rat Roc-Roc's Avatar
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    I had a similar problem on my 85K100rs. I change out the fuel filter twice, and the problem will go away for a day or two. I went to three dealers. It finally died out on the middle of no where. The fuel pump died. Your problem is intermitten right now . When it goes it will blow the fuel pump fuse.
    ROC-ROC
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  9. #9
    Registered User WalterK75's Avatar
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    Quote Originally Posted by argent brick View Post
    By "heat sensor", do you mean the one that checks coolant temp. and sends info to the fuel injection?
    Yes.
    Walter

    G. K. Chesterton wrote - "The traveller sees what he sees, the tourist sees what he came to see."

  10. #10
    Registered User 58058D's Avatar
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    BCKRider, now that you have replaced the fuel filter and provided additional information, perhaps you should check the spark plugs. You indicated that your fuel consumption has increased, perhaps you have fouled a plug? Do a search and look for threads that tell you how to pull your injectors and test their spray pattern, easy to do, but always have your fire extinguisher nearby. So, essentially, the old adage of air, spark, fuel...each is needed for combustion. Track down which is not present.
    Jim Douglas '00 K1200RS >135,000 miles my primary bike again,
    Gone: '09 K1300S sold @ 22k mi, '93 K1100RS traded @ 78k mi, '85 K100RS sold @ 44k mi
    '06 Kaw 650R track bike sold
    http://www.seagullbb.com/

  11. #11
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    Quote Originally Posted by BCKRider View Post
    2. the idle is slower than normal and the engine just sounds rough when it lacks normal power and 3. the change from full power to little power and vice versa is instantaneous - it is just as suddenly running well as running badly.

    Any thoughts on what to check next?
    Sounds electrical/spark related.

    Take an inductive timing light or an inductive spark checker and test at each plug wire while it is running poorly. If you find two cylinders not firing properly, see if they are on the same coil. Could be a bad coil.

    Could also be one of the pickups on the Hall Effect sensor starting to fail.

    Insure that the plug to the FI computer is solidly connected. Unplug it and replug it in several times to clean the contacts. Make sure it "CLICKS' when you plug it in.

    Try unplugging the Throttle Position Switch and see if it runs OK with it unplugged.




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    Lee Fulton Forum Moderator
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  12. #12
    Kbiker BCKRider's Avatar
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    New information

    When the mechanic removed the cover over the spark plugs and wires, the answer seemed obvious: somebody in re-installing that cover had pinched the #2 spark plug wire and a piece of the insulation had worn off. Seemed a perfect explanation of why the bike was running on three cylinders and using a lot of fuel, though not so perfect in explaining why it was an intermittent problem. A wrap of electrician's tape over the damaged area we both thought would fix the problem, at least temporarily. Temporary turned out to be about 3 miles. Then I remembered the bike had been running well when I brought it into the shop. When it started running badly again, I brought it back to the shop.

    Next, the mechanic shut off the fuel injector to the #2 cylinder and started the bike. NO CHANGE IN THE BAD RUNNING. His thought is that the problem is definitely connected to that one cylinder. So maybe the spark plug wire - which tested OK on his meter - really wasn't OK with "real world" current, or whatever. (The owner of this garage found out that it would take about three weeks and $85 to get a BMW replacement spark plug wire, and since that is the rest of my riding season, I asked if they could come up with a fairly cheap and useable solution. They tried to fashion one. Didn't work.) Rode the 16 miles home on three cylinders - I think. Can this bike do 60 mph on two cylinders? I believe plugs two and three are on the same coil and these guys were into overtime.

    Possible problems already suggested are: 1. fuel pump (reject that as we are down to one dead cylinder,) 2. heat sensor (reject that as I would think it would effect all cylinders,) 3. #2 fuel injector (reject that, as I don't see how it could cause the intermittent problem,) 4. pickup on Hall Effect Sensor starting to fail (can this affect one cylinder?) 5. plug connection to the fuel injection computer (something simply we haven't tried, but can this affect only one cylinder?) 6. Throttle Position Sensor (can this affect one cylinder?) 7. spark plug (#2 looks OK, but could it be as simple as that?)

    I hope you bright guys so familiar with K bikes can point me and mechanics I trust in the right direction. You are best thing about my membership.
    Doug
    1992 K100RS

  13. #13
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    Doug,

    Electrical tape will not insulate the thousands of volts that are going through the spark plug wire. It sounds like it is arcing to ground through the break in the wire instead of through the spark plug. Get the bike in a very dark place with the plate that covers the spark plugs off and run it. You might see the arcing. If not, shut off the bike and spray a LIGHT mist of water in the area with a spray bottle, then try again. Good used wires can be purchased from any of the several BMW bike recyclers.



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    Lee Fulton Forum Moderator
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  14. #14
    A bozo on the bus deilenberger's Avatar
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    And if it's arcing to ground through a break in the insulation - the other plug must be firing, since that's the path to ground. So - it's running on 3 cylinders despite the double-ended coils.

    One thought - K100 cables are a resistive cable. They should measure 5K Ohms from end to end (within about 5% actually)..

    If you try to fashion a replacement, it also should be resistive. There is resistive wire made, and solid plug ends meant to mate to them. Dunno about what the resistance is per/foot, so that might be an issue. A better bet might be wire-core wire, with a 5K Ohm plug cap..

    Best bet - as Lee said - a good used wire. They rarely actually fail, the quality is excellent on them, and on the K100 (unlike the K75) you can measure them to make certain they're good.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
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  15. #15
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    And since they rarely fail, recylers have a ton of them that few people want to buy, thereby the price should be low.

    Try beemerboneyard or Repsycle, both of who advertise in the Owner's News.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

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