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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: 3dachshunds on May 20, 2026, 08:13:42 PM

Title: Does this engine sound normal to you?
Post by: 3dachshunds 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

Title: Re: Does this engine sound normal to you?
Post by: Filmcamera 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.

Title: Re: Does this engine sound normal to you?
Post by: Laitch 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?

Title: Re: Does this engine sound normal to you?
Post by: 3dachshunds on May 22, 2026, 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.