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Thread: 98 R1100RT, horrible sputtering!

  1. #1
    It's a way of life! oldnslow's Avatar
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    98 R1100RT, horrible sputtering!

    Ok, I had a vaccuum situation with my bike; the big 'woosh' sound when I opened the filler. Bike was running poorly at idle and would sometimes die, but ran good going down the road.

    Started it today and it ran horribly.

    Did the canisterectomy, did nothing else. Now the bike runs still horribly, if not worse. Cuts out, sputters, wont idle, starts hard, won't run down the road with out cutting out and bucking and sputtering. When I try to hold the idle speed at any RPM while in nuetral, the engine will sputter, after fire, (backfire through the exhaust) and rpms will surge up and down wildy.

    After removing the cannister, I gently blew into the hose and I could hear and feel the air blowing into the bellows looking thing inside the tank.

    I no longer have the 'woosh' sounf when I open the tank.

    I touched no carb settings or any electrical settings.

    I am testing and running it naked (the bike not me) with out tupperware, if that makes a difference.

    The airbox is sealed and the filter is new and the temp sensor in the air box is connected.

    It has fresh gas from a trusted dealer with 6 oz of Techron added.

    The bike ran perfectly other than the idle issues prior to this.


    Suggestions and procedures please.

    The bike is very low miles, 18000, and had 12000 mile service performed by a dealer about 4 years ago
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  2. #2
    Lucky MotorradMike's Avatar
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    Is the right side throttle cable tight with the throttle closed?
    Mike Marr
    1978 Yamaha XS750 (Needs rings), 1996 BMW R1100RS, 2004 Honda CRF230F

  3. #3
    It's a way of life! oldnslow's Avatar
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    Quote Originally Posted by MotorradMike View Post
    Is the right side throttle cable tight with the throttle closed?
    Both side have a very small amount of slack in them. About 5 mm of slack when I push on the exposed cable before it causes the butterflies to move.

    Again, the bike ran wonderful other than the idle issue and the tank vaccuum situation.

    Im guessing fuel filter? Maybe in tank fuel line damage caused by the vacuum in the tank?

    The vacuum was VERY strong. So strong that I had to pull the lid on the filler up by the key flap.
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  4. #4
    Registered User roger 04 rt's Avatar
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    Quote Originally Posted by oldnslow View Post
    Both side have a very small amount of slack in them. About 5 mm of slack when I push on the exposed cable before it causes the butterflies to move.

    Again, the bike ran wonderful other than the idle issue and the tank vaccuum situation.

    Im guessing fuel filter? Maybe in tank fuel line damage caused by the vacuum in the tank?

    The vacuum was VERY strong. So strong that I had to pull the lid on the filler up by the key flap.
    There are several possibilities. From the sound of it you have a very lean or rich mixture, but it could be spark I suppose.

    If it's not too hard for you and you can do it safely, I would begin by finding a way to measure the volume of fuel returning from the pressure regulator to the tank. It should be 1 1/2 to 2 liters per minute at idle. Your pressure regulator is probably fine so if you get the correct return volume you will know that your pump, filter and internal hoses are good. This is harder to do if you don't have quick disconnects (QDs) but keeps you from having to pull and drain the tank. Be safe if you do this.

    You might try pulling Fuse 5 for a few minutes to reset your Motronic, and then see how it runs.

    If you have QDs I've had the return line QD open and cause very poor running.

    You've checked your cables but I would double check that they're seated and the throttles are opening simultaneously.

    Next up would be your HES or coil.

    Others will surely have some good suggestions as you start to narrow things down.

    RB

  5. #5
    It's a way of life! oldnslow's Avatar
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    Reset the #5 fuse and it runs perfect!

    Thanks!!!
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  6. #6
    Registered User roger 04 rt's Avatar
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    After making a lot of measurements on my 1150 I've been wondering if the earlier 1100 uses a technique called Adaptation. The answer from your problem makes it clear that does.

    Here's what I think happened: When your filter got clogged, the tank built the vacuum that you reported. With a vacuum in the tank, the pump couldn't deliver enough pressure to the fuel distributor. For a while, the Motronic adapted to the situation and added fuel; but eventually the vacuum grew to the point that the Motronic couldn't adapt and your bike started running lean.

    However during the time it was Adapting to the low pressure, it was storing correction information in the Motronic that said it needed to add fuel both Open Loop and Closed Loop (using the O2 sensor). After you release the vacuum and fix the problem, the Motronic uses the Adaptation Values it learned during the vacuum problem but now it is so rich that it misfires. The misfiring looks like a lean mixture and the Motronic still sees oxygen in the exhaust from the misfire and keeps adding the maximum fuel.

    You fixed the problem by resetting the Motronic and clearing the incorrect Adaptation Values. Your Motronic will slowly build new values when the engine is warmed-up and you're driving with a steady hand on the throttle. The more RPMs and throttle positions you run, with a steady throttle, the quicker it will learn.

    Let us know if it happens again. If it does, you may have another problem, possibly an O2 sensor failure.

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