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Author Topic: K75 Running on 2 at idle and 3 when above 1500  (Read 2068 times)

Offline Steveo277

  • Curious
  • Posts: 4
K75 Running on 2 at idle and 3 when above 1500
« on: January 05, 2023, 09:17:39 AM »
Hey all,

So I have my K running after 5 years of rebuild and it runs beautifully above 1500 but at idle she only runs on 2.

It has new coils, plugs, changed both ICU's, new injectors, fuel lines. It runs at 36 psi fuel pressure.

It has me stumped.
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Offline Steveo277

  • Curious
  • Posts: 4
Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #1 on: January 05, 2023, 09:19:51 AM »
Forgot to add a picture of my bike.
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  • K75

Offline Laitch

  • Faster than a speeding pullet
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Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #2 on: January 05, 2023, 11:32:38 AM »
Do a noid test on #2 injector electrical connection to determine if that's the source of the intermittent problem. If the light isn't flashing at idle but flashes at higher revs, there's a wiring connection problem to that injector. This video explains the procedure. As mentioned in the video, noid kits possible can be gotten at major auto parts stores but you only need the light for Bosch injectors.
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline KCinSB

  • ^ Proficient Motobricker
  • Posts: 260
  • Still learning about Bricks from this site!
Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #3 on: January 05, 2023, 11:12:46 PM »
Since I’ve never seen a Noid tester, or know what a Noid is, I started to ask how you know its only running on #2 at idle,……. But reading again, I think you mean it is only running on 2 of the 3 cylinders correct?
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  • Santa Barbara, CA
  • SOLD
No good turn goes unpunished, but it's fun to keep trying.........
1993 K1100RS, with LT Rack&Case, some old BSAs and Triumphs,... some even run!! Recent Dark Side foray... '65 XLCH tractor.

Offline Chaos

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Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #4 on: January 06, 2023, 01:34:44 AM »
Compression test?
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  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Martin

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  • Posts: 4475
Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #5 on: January 06, 2023, 03:00:38 AM »
From a cold start the header pipe of the non-firing cylinder will be colder to touch as it warms up. You can also use a laser temperature gun which is a worthwhile addition to any tool kit.
Regards Martin.
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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline frankenduck

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  • Posts: 5511
Re: K75 Running on 2 at idle and 3 when above 1500
« Reply #6 on: January 06, 2023, 04:21:41 AM »
If you've replaced all of that stuff and swapped th ICU and L-Jetronic then the next link in the chain is the FI wiring harness - 61111459978. Do you have a spare one of those to try?
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Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
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