Author Topic: Does this engine sound normal to you?  (Read 109 times)

Offline 3dachshunds

  • Motobrick Curious
  • Posts: 30
Does this engine sound normal to you?
« on: May 20, 2026, 08:13:42 PM »
I’ve been working on 1992 k100rs since last fall and finally got the bike running (clogged injectors). I was super excited that I finally got it running, but didn’t actually ride until now. (New fluids, new tank innards, new spark plugs). I don’t like how it sounds at idle. It sounds to me either misfire or a problem with crankshaft bearings. It has hesitation at about 4.5-5k RPM, around 80MPH. It starts feeling sluggish. Please let me know what do you think.


https://drive.google.com/file/d/1Qqn2XgcRyBtIj7QKubrpFsX3cLhWUb_L/view?usp=drivesdk
  • USA
  • 1992 BMW K75, 2013 Triumph Tiger 800 roadie

Offline Filmcamera

  • ^ Quintessential Motobricker
  • Posts: 1480
Re: Does this engine sound normal to you?
« Reply #1 on: May 21, 2026, 03:44:30 PM »
That does not sound right to me!  That intermittent thunk is not something my 1991 K1000 RS does.  I sounds like you might be in three cylinders.  If you have a gun type thermometer try measuring the heat of the four exhausts as they come out of the engine.  If one is much cooler it might not be firing right.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2022 Triumph Tiger 900 Rally Pro
Poserbricker

Offline Laitch

  • Faster than a speeding pullet
  • Administrator
  • ^ Quintessential Motobricker
  • Posts: 11424
Re: Does this engine sound normal to you?
« Reply #2 on: May 21, 2026, 10:15:43 PM »
Among several causes, defective fuel injectors and faulty coils or coil connections can cause knocking. Were all the injectors replaced, or were they professionally cleaned?
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline 3dachshunds

  • Motobrick Curious
  • Posts: 30
Re: Does this engine sound normal to you?
« Reply #3 on: Today at 12:01:41 AM »
I cleaned injectors by energizing them directly from battery and spraying brake cleaner simultaneously. Probably damaged one or more during the process. I hope that’s the root cause. New injector set should arrive next week from Euromoto.
  • USA
  • 1992 BMW K75, 2013 Triumph Tiger 800 roadie

Tags: k100 idle hesitation