knocking when K75 is in neutral, clutch out

[jayedee]

Thought I'd share this since I was unable to find any posting with a similar experience.  My bike is a '92 K75 with 40k on it.    I bought the bike with 28k ; the clutch was always stiff but manageable, and I didn't know it should have been different.  I changed the cable, lubed the linkage, and lived with it.

I gradually became aware of  a knocking sound when the bike was in neutral, clutch engaged.  The knock gradually went from being barely noticeable to being worrisome. (What follows is from a post I put on a different forum.) The symptoms : knocking sound in neutral with clutch engaged; quiet when cold but knocking got louder as engine warmed; and, in my case, stiff clutch release. The service manager at my local dealer figured it might be gear knock and recommended heavier oil, clutch linkage lubrication, and cable replacement as the first things to try.

When those didn't work, I pulled the tranny and looked at the clutch and spring. Both looked good, but the diaphram spring was hard to compress. I replaced both clutch and diaphram. Result: noise completely gone, easy clutch pull, excellent shifting (about 1000 miles now).  My theory: the diaphram spring was sticking in places, or just warping  as the bike warmed, causing the clutch-disengage pushrod to knock back and forth when the clutch was out (especially noticeable when bike was in neutral).

[Tuco]

Not the remedy I expected!

[F14CRAZY]

Was it anything like this?

https://www.facebook.com/f14crazy/videos/10152470976647908/?l=664406627236583586

I've noticed this for a while but haven't done anything to fix it

[Laitch]

My bike sounds like that, too, F14Crazy, and has for the last 24K miles. I like its pleasant early-industrial revolution beat and besides that, I subscribe to a time-tested Cuban philosophy—if your problems have solutions, why worry, and if your problems don't have solutions, why worry? I have both fixed the problem and given myself an on-going sense of accomplishment with a three-part treatment strategy—by keeping the bike on the move, by squeezing the clutch lever, or by shutting off the engine—any one of which instantly eliminates the condition.

On the other hand, MAX is having a sale.

[johnny]

greetings...

problems with solutions and problems without solutions... both go better with weed butter cookies... so does motobricking...

j o

[F14CRAZY]

My bike sounds like that, too, F14Crazy, and has for the last 24K miles. I like its pleasant early-industrial revolution beat and besides that, I subscribe to a time-tested Cuban philosophy—if your problems have solutions, why worry, and if your problems don't have solutions, why worry? I have both fixed the problem and given myself an on-going sense of accomplishment with a three-part treatment strategy—by keeping the bike on the move, by squeezing the clutch lever, or by shutting off the engine—any one of which instantly eliminates the condition.

On the other hand, MAX is having a sale.

Well I figured whatever is making it knock at idle with the clutch out probably exists when the bike is in gear with the clutch out. I've also put on about that many miles with the condition and nothing bad has happened yet  :riding:

I suppose I could replace the diaphragm spring next time I lube the clutch splines

[Laitch]

both go better with weed butter cookies

Baked with 100% cold-pressed extra virgin cannabinoil sanctified by Rev. Creflo Dollar.

[K1300S]

hmmm.  my K75 with 35k has a rattle, clutch out, between 1200-2000 rpm.  sounds like it is coming from rear of engine, front of tranny area. can really hear it as you pull off in 1st.  wonder if same issue.  using redline MTL in the gearbox. will have to get out the stethoscope to narrow down.  (NOT while riding!)

[F14CRAZY]

hmmm.  my K75 with 35k has a rattle, clutch out, between 1200-2000 rpm.  sounds like it is coming from rear of engine, front of tranny area. can really hear it as you pull off in 1st.  wonder if same issue.  using redline MTL in the gearbox. will have to get out the stethoscope to narrow down.  (NOT while riding!)

that sounds like the timing chain rattle...they all do that, even when brand new

[Laitch]

That's a different noise than the idle beat, Marshal. Keep the revs up; don't let it lug. As F14 has stated, TADT. Well, mine does anyway, and apparently F14's, too.

[K1300S]

TADT, aye!   thanks guys.  calibrating my ears as to what is normal and what is oh, oh!

[jayedee]

F14, that's the noise.  The knocking in mine was pretty soft at startup but would get louder as the bike warmed.  My guess is the noise was the clutch pushrod banging against the throwout bearing as the diaphram spring warped (or whatever it did as the bike warmed).  Incidentally, and probably unrelated, my bike started jumping out of 2nd gear several thousand miles after the noise appeared.  I replaced the tranny and ran with the knocking (which I had hoped would disappear with the new tranny--but didn't) several thousand miles before I pulled the clutch for a look.

[jayedee]

One more note:  The replacement tranny was new (old stock) so, since the knocking continued as before, it seemed pretty clear to me that the tranny was not the cause of the noise.  And it wasn't.

[F14CRAZY]

Would you say that replacing the diaphragm spring fixed it?

[jayedee]

Yes.  However, I also changed the clutch disk (as advised by the shop manual--change spring, change clutch--even though the original looked fine) and greased the input shaft (which had also been done when I put in the new transmission about 4k miles previous--to no effect).  So it's possible the clutch disk was the problem, but unlikely.  The spring had to be the culprit in the stiff clutch lever problem, and the fact that the pushrod pushes on the spring/diaphram on one end and on the throwout bearing, which seemed to be the source of the knocking, on the other makes me STRONGLY suspect the diaphram spring.

So, again, yes.  It definitely worked for me.