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Thread: Low RPM Stall/Stutter after TPS reset

  1. #1
    Registered User 148491's Avatar
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    Low RPM Stall/Stutter after TPS reset

    '02 1150GSA

    Just installed Dan Cata's Throttle Body Kits (both). I positioned the TPS as closely as I could to the pre-rebuild spot. After getting an initial 1.06v reading and fiddled around until it was .36v. Pulled the Motronic Diagnostic Plug fuse for a minute then turned the ignition and cranked the throttle 3 times.

    The bike started immediately and the Throttle Bodies were nice and quiet (Thanks Dan )

    Needless to say some other adjustments were needed so after a brief ride to get it up to temp I synced the cables and the bodies and off for another test ride.

    Results:

    Bike idles nicely at 1100rpm and at speed pulls nicely when at speed. The problem is at the point when I just start to move at low rpm from a stop or slow turn. It was faltering and I had to give it more throttle or it would certainly die. Again this is just at that low rpm from about 1200 to 2k.

    When I got back I checked the cable sync and throttle bodies with a manometer and they were both good. From the 1100rpm idle in neutral I just slowly rolled on the throttle to replicate my earlier problem only in a stationary position. When it got to 2k rpm it stalled. Now had I throttled up more quickly it would have made it through that problem area.

    Is this a TPS issue, should I recheck the voltage on the TPS, does it take more than one 5 mile ride for the Motronic to learn the throttle range?

    So......someone kick me in the right direction for this glitch.
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

  2. #2
    Registered User roger 04 rt's Avatar
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    There are a lot of possibilities. Let's try to narrow it down.

    Is the right hand throttle cable seated correctly in its retainer just above the TB?

    When you said you pulled the Diagnostic Plug fuse (there isn't one) I think you were referring to Fuse 5 which powers the Motronic. Are you certain you removed the right fuse? When you later turned the ignition on and twisted the throttle twice was the fast I'd.le lever down?

    It sounds like you have a TPS/throttle stop screw/Air bypass (BBS) alignment issue.

    With the fast idle lever off (down), do you have 1 mm slack in the throttle cable on each side? Is each throttle body throttle shaft coming to rest against its throttle stop screw?

    How many turns is each BBS screw from bottom?

    Are both throttle plates coming off the stop at exactly the same moment?

    As you increase the RPM from 1100 does the rpm increase smoothly and then just stop at 2000?

    I'm sure you'll get other ideas soon

  3. #3
    Registered User 148491's Avatar
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    Thanks Roger. Yes it was Fuse #5 and the battery had also been disconnected the night before. The fast idle lever was down when the throttle was opened. The cables are also seated correctly in the knurled ferrules.

    As far as the other good suggestions you mentioned I'll have a look in the morning and go over them then.

    The flat/stall area in the rpm range is in between say 1200 to 2k rpm. It did actually stall the once when I was off the bike and slowly spooled it up and that was at 2k. While riding it wanted to stall/falter but I just gave it a bit more throttle and it got over that threshold and pulls as normal. It's must that narrow range at low rpm.

    Thanks again
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

  4. #4
    Registered User roger 04 rt's Avatar
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    Okay, good luck tomorrow. I hope that it becomes obvious at some point.

    For things like this I set my GS-911 up to log the Motronic data to a PC .CSV file and then just look through the data to see what's happening.

    In this case I would look at the TPS data stream, RPM and injection time. TPS angle, RPMs and injection time should all be increasing as you open the throttle--although without a load the injection times don't change much in the 1100 to 2500 range, they're around 2 mS if memory serves me correctly.

  5. #5
    Registered User 148491's Avatar
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    Follow up

    Everything was fine prior to me putting the bodies back on etc with no change to the CCP etc. I've been reading for hours now and what I'm coming back to is "do I have slack in the throttle cables?"

    The right cable had sufficient slack and the lock nut is about mid point on the threaded portion of the cable adjuster. When I reconnected the left cable I did have difficulty in getting 'any' slack and in fact threaded portion is screwed in to the max with the lock nut touching the knurled ferrule.

    Sitting here now I'm trying to figure out why I don't have more than enough slack with it screwed all the way in. Can this lack of slack cause this low rpm stall issue?
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

  6. #6
    Registered User roger 04 rt's Avatar
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    It also caught my attention that your TPS was initially at a volt. Sounds like something happened on the left either during TB assembly, or to the left hand cable (is it mis seated in the Bowden box) or reinstallation of the pulley. Not sure but I bet that is your culprit.

  7. #7
    Registered User 148491's Avatar
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    Morning Roger....I will re measure the voltage on the TPS this morning but first I will revisit the left hand cable. It is strange that it's pretty much screwed all the way down and even then not much slack to speak of. You'd think after 97k Miles the cables would be stretched if anything and half to be unscrewed more leaving more thread exposed instead of the other way around.`
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

  8. #8
    Benchwrenching PGlaves's Avatar
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    You changed the TBs - not the cables. If the cable was long enough for a normal adjustment setting (not screwed all the way in) before you swapped the TBs then it ought to still be long enough. So, it seems to me that the outer sheath is not properly seated at the bellcrank box end, effectively lengthening the sheath making the inner cable too short at the TB end.

    I think you need to dig into the bellcrank box end of the cables to ensure that cable didn't get pulled out somehow. Big pain - yes, but I don't think you will find the problem until you do that.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  9. #9
    Registered User 148491's Avatar
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    Paul:

    Thanks....I assume the bell crank end is in the bowden box under the abs etc?

    I just finished disconnecting the left cable and then carefully reconnecting it again. I also re did the voltage on the tps....now it's off for a test spin.
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

  10. #10
    Registered User roger 04 rt's Avatar
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    When you did that did you find more length now at the left side adjuster?

  11. #11
    Registered User 148491's Avatar
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    Solved!

    Well I went out the shop first thing and took the throttle cable off the throttle body and carefully re-installed it. The cable was feeding onto the pulley but it's possible the underside cabling and the end stud weren't seated exactly where it should have been.

    I did get some slack so I adjusted it for about 1 mm.

    When I had put the TPS back on the TB, post rebuild, I did the initial adjustment and got it at .36 v. Of note, the TPS wasn't positioned anywhere close to where it had been prior to removal for rebuild. So I pulled back the boot and re tested the TPS and got it at .36 v.

    After the fuse removal/throttle crank blah blah I started it up and took it for a spin. When at working temp I started to some slow speed turns and starts etc and my stall/falter problem was Gone!!

    So whether it was the cable or the TPS or a bit of both it's fixed. I did the cable and TB sync with the manometer and it's running as smooth as silk......phew! I wasn't relishing getting into the Bowden Box to see if the left cable had unseated there.

    Thanks to those who replied and kicked me in the right direction!
    Last edited by Ron from BC; 02-17-2013 at 10:07 PM.
    '02 R1150GSA
    '76 R90/6
    '64 R50/2 - "Gone but not Forgotten"

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