Author Topic: Stuttering under part-throttle  (Read 4572 times)

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 3284
Re: Stuttering under part-throttle
« Reply #50 on: May 18, 2018, 04:19:46 AM »
When my sensor played up, it was the connection not the sensor.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline E30_Crazy

  • ^ Motobrick Curious
  • Posts: 61
Re: Stuttering under part-throttle
« Reply #51 on: May 18, 2018, 10:50:19 PM »
The cutting off and not starting while hot presents a temp issue. Just looked more carefully at a more detailed wiring diagram. I had only checked my temp sensor and wiring at the FI computer plug. Gonna check the other signal and wiring going to the temp switching unit, the unit itself if I can, and the fuel injection relay. I can bear the pump running while cranking, and it sometimes want to start (when hot) but then dies. Pump or injectors may be cutting off as a result of bad temp input somsomewhere.


If these all check out, I'm back to the FI computer being shot (for a second time)
  • Newport News, Virginia
  • '85 K100

Offline Martin

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  • Posts: 3284
Re: Stuttering under part-throttle
« Reply #52 on: May 18, 2018, 11:46:40 PM »
If the sensor is playing up the spark plugs will be wet. With the plugs out and earthed ( failure to earth the s/plugs can result in damage to ignition module) the check the spark, but be careful not to ignite the excess fuel. Remove the fuel pump fuse #6 while doing the test.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline E30_Crazy

  • ^ Motobrick Curious
  • Posts: 61
Re: Stuttering under part-throttle
« Reply #53 on: May 19, 2018, 01:56:56 AM »
Temp sensor checks good at the temp switching unit. Wiring from temp sensor plug to the unit it good as well. Nothing burnt up inside the unit. Wiring from Temp switching unit to the FI relay checks good. I may try and pick up a new FI relay. Wondering if something inside is failing after carrying the power load for an amount of time.... And I may have the wrong one anyways. The part number returns as a BMW car relay. Reading around here and other forums, the K100 (or at least early ones like mine) had points reversed, and that the double 87 shouldn't have an "A" and/or "B" attached (double output vs alternating output IIRC).
  • Newport News, Virginia
  • '85 K100

Offline E30_Crazy

  • ^ Motobrick Curious
  • Posts: 61
Re: Stuttering under part-throttle
« Reply #54 on: May 19, 2018, 08:30:07 PM »
Tested the fuel injection relay, and it turns out that it is a dual output relay.


Bike starts and idles fine. But after warming up a bit, if I try to rev past 4 or 5k rpm, and it stutters too much, or I try to ride it, it shuts off and won't start again until it cools off some. Temp sensor, and all wiring after it on both paths checks good. I'm thinking the FI computer has failed for a second time. If the signals and sensors are all correct, it must be the interpretation part that is bad.
  • Newport News, Virginia
  • '85 K100

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 4928
Re: Stuttering under part-throttle
« Reply #55 on: May 20, 2018, 07:08:47 AM »
Test the coils according to the method within this guide. It's located just after the Hall sensor test. Have you done that yet?
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

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