Author Topic: 1989 K75 engine rattle/knock. (Read 181868 times)

mystic red · « **Reply #25 on:** May 30, 2016, 02:41:05 PM »

When I first bought my 1100 I noticed a knock just like that. Took it to the dealer who had a great service manager back then. He said, after listening to it, "sounds like a good strong K bike." That was 50 thousand plus miles ago. Just saying.

K1300S · « **Reply #26 on:** May 30, 2016, 02:55:40 PM »

Here is mine

Rhodes rash · « **Reply #27 on:** May 30, 2016, 03:33:19 PM »

Gryphon's right. I went through the huge effort this winter tracking 'the noise'. I was convinced it was the anti-backlash gear assy. Took the engine out of the bike ('91 K75RT), opened up its guts and found nothing wrong in there. It appears that torquing the retaining nut on the output shaft/clutch housing does the trick as 'the noise' is gone now. Could have saved myself a HUGE amount of time and effort by doing the torquing along with a spine lube. You can check out a long thread on this subject on the K100 forum. Look for the thread 'engine clatter'. (I hope I haven't breached protocol by making this reference)

gone_ape · « **Reply #28 on:** May 30, 2016, 03:55:44 PM »

Mlytle, that's the exact same sound mine makes, but mine is 'slightly' quieter.....Rhodes, I will take yours and Gryph's advice to clean mating surfaces and re-torque the clutch to output shaft nut to the higher factory spec.

I'll relax, Mystic !!! Sounds like these are psychological mind humpty-humps..... I'm going to get after this this winter and report back then...thanks all...

The Mighty Gryphon · « **Reply #29 on:** May 30, 2016, 04:06:32 PM »

My simian buddy, I am willing to bet that when you di your clutch work you got a bit of oil on the interface between the clutch hub and the balancer shaft. I suspect that is all it takes to let them move and bang around. Any clutch work including an o ring replacement will break the connection between the shaft and the clutch hub and open the door for the motion and the clank.

I have a photo of the parts where the clank comes from. I was able to make the noise with them on my bench when the engine was apart. I can't post them for a couple days because they are on a different computer.

It should be an easy fix, you don't even have to take the engine out of the frame.

gone_ape · « **Reply #30 on:** May 30, 2016, 05:58:25 PM »

Gryph....I've just had that 'Ah-Hah' moment......being careful about the clutch hub torque, i gave zero thought to oil fouling of the interface to the balance shaft...as i....wait for it.....oiled up everything there as to not oil starve the bearing/seal relationship until engine oil pressure took over............*takes palm of hand - smacks forehead*.....but then again, without this forum, how would one know about this little delightful delicacy ??? Thank you for your insight. I know exactly what to do now......

gone_ape · « **Reply #31 on:** May 30, 2016, 06:22:41 PM »

You know, Johnny, I've listened to every last you tube vid I could find of folks revving their bikes off idle and could not come to the same conclusion you have, as I just could not hear it...so my feeble mind wandered to this being a specific issue....and of course due to my 'complete waste of time' research tactics, the end result is just ride the thing.

That being said, I now realize that I just need to whack the throttle, as you so eloquently say....thanks

K1300S · « **Reply #32 on:** May 30, 2016, 06:26:56 PM »

Quote from: johnny on May 30, 2016, 06:05:16 PM

the only motobricks i have heard that did not sound like that were the one not running...

I have another k75 with same mileage as mine in my shop. Whisper smooth. Zero knock or rattling.

Laitch · « **Reply #33 on:** May 30, 2016, 06:35:57 PM »

Quote from: mlytle on May 30, 2016, 06:26:56 PM

I have another k75 with same mileage as mine in my shop. Whisper smooth. Zero knock or rattling.

How many miles and which year, Marshall?

I'm in agreement with j o and mystic red, I think. I do understand though, the quest for perfection. My good fortune is that I've accepted it's out of my grasp regardless of how convenient it is for others to access.

With that in mind, what seems to be the topic here is that hollow, low-pitched, rattle occurring during a slow transition from idle to slightly higher revs. My bike did that when I first got it but I haven't let it do that since I got a message from the mothership via my dentition that said, "more revs, more revs." Timing increased revs with the release of the clutch damps that noise regardless of its origin. It just isn't there when I shift with enough revs—that doesn't necessarily mean whacking the throttle—as fun as that is. It just means more revs quicker.

If there is another sound that is being discussed other than that one, thankfully, I can't hear it.

Laitch · « **Reply #34 on:** May 30, 2016, 06:37:58 PM »

Thanks for the audio, Marshall.

K1300S · « **Reply #35 on:** May 30, 2016, 06:57:42 PM »

93/94 years. 35k miles.

Had to moto around at 5-10mph in first gear a bit last weekend. Rattle was very annoying and un-bmw like.

Laitch · « **Reply #36 on:** May 31, 2016, 07:30:05 AM »

Quote from: mlytle on May 30, 2016, 06:57:42 PM

Rattle was very annoying and un-bmw like.

That I can understand, Marshall, especially because you've been involved with race tuning BMW engines and are accustomed, probably, to getting submission from them. Poking along on my K is my least favorite sport. I don't allow it to rattle though. I'm in the clutch friction zone and on the back brake, revving, and slipping along. The only thing that makes it interesting is testing how long I can balance at a standstill.

Mine will quietly behave at low speed but whenever I can briefly accelerate I slip the clutch to raise the revs. Mostly, I avoid city traffic, parades and funeral corteges when on the K.

That whisper-quiet K is one I'd like to meet but I'm satisfied with the one I've got.

The Mighty Gryphon · « **Reply #37 on:** June 02, 2016, 10:01:14 PM »

Neither of my K75's clank anymore. The Yellow one never did, but it only has 36k miles. The Red one has 71K miles and has did it as long as I've owned it which is since 55k miles. The Red one clanked a lot at idle which made it sound like a piece of shit when I was sitting at lights or when starting the engine before riding out.

Why the F should I burn up my clutch in traffic to stop the clank? Slipping the clutch while I wait for the tan Buick in front of me to accelerate enough to let me get above 2000 rpm in 1st isn't my idea of good engine management. I used that brick for commuting and as a result got stuck in stop and go quite often.

Laitch · « **Reply #38 on:** June 02, 2016, 10:03:04 PM »

Quote from: The Mighty Gryphon on June 02, 2016, 10:01:14 PM

Why the F should I burn up my clutch in traffic to stop the clank?

You shouldn't burn up your clutch, Gryph. It smells bad when you do that.

gone_ape · « **Reply #39 on:** June 02, 2016, 10:35:41 PM »

So I'm going to tear into this in about a week...I've ordered up the requisite o ring, nut and 'compression ring' and my question to you all is:

Whilst I have this apart, anything you'd like pics of, (no wait, that sounded just wrong) or check and then relay back anything else in there for your own piece of mind if you're considering doing this?

Laitch · « **Reply #40 on:** June 03, 2016, 03:40:47 PM »

Quote from: gone_ape on June 02, 2016, 10:35:41 PM

So I'm going to tear into this in about a week...I've ordered up the requisite o ring, nut and 'compression ring' and my question to you all is:

Whilst I have this apart, anything you'd like pics of, (no wait, that sounded just wrong) or check and then relay back anything else in there for your own piece of mind if you're considering doing this?

You could start a thread in the Projects section and photograph the job in its stages with a description of what you encounter and how you tackle things. If you run across any foreign currency, critters or unidentified objects in there, post photos of those, too.

gone_ape · « **Reply #41 on:** June 03, 2016, 09:02:31 PM »

Kicked that idea around. but one would think taking the clutch off has kinda been played through posts - here and elsewhere, right? My thoughts were if someone dealing with this specific issue had curiosities... I dunno....

kennybobby · « **Reply #42 on:** June 04, 2016, 07:44:13 AM »

hey G_A,

It would be interesting and helpful to know if you can manually cause the sound to occur using a lever or bar or wrench to rotate the shaft back and forth at the earliest stage before you get all the way to pulling the bottom. Like can you make the sound by rocking with the pressure plate attached, or after the clutch is removed and rocking the output shaft at the flange, etc. Just as a diagnostic method to indicate that the anti-backlash spring is the culprit before doing the full-blown disassembly. thanks, kb

Laitch · « **Reply #43 on:** June 04, 2016, 07:54:48 AM »

Quote from: kennybobby on June 04, 2016, 07:44:13 AM

It would be interesting and helpful to know if you can manually cause the sound to occur using a lever or bar or wrench to rotate the shaft back and forth at the earliest stage before you get all the way to pulling the bottom. Like can you make the sound by rocking with the pressure plate attached, or after the clutch is removed and rocking the output shaft at the flange, etc.

Kind of like this, kennybobby? This may be the video Gryph mentioned earlier.

gone_ape · « **Reply #44 on:** June 04, 2016, 10:05:50 AM »

That's a clack right there..... But according to what Gryph and Rhoads were saying, this isn't transmission related.....(YMMV).
KB, you bring up a good idea...once the tranny's pulled, I'll attempt to see if the sound can be replicated by manual manipulation...I gather I'm looking for some kind of end float scenario at the flywheel....
I'll report back with my findings (if any). And IF I do find a culprit audibly, then Laitch, I think your idea of a new thread post would be in order.

The Mighty Gryphon · « **Reply #45 on:** June 04, 2016, 10:43:27 AM »

Same noise I had, but mine was found to be from the dogs on the balance shaft hitting the sides of the slots in the output gear. Because of the balance shaft on the K75 it is unique to that engine and not a problem on the K100's.

I would expect the clacking in the video to stop when the clutch is pulled in and the transmission is in gear. On my bike the clacking was there all the time whether the transmission was in gear or not or whether the clutch was in or out.

gone_ape · « **Reply #46 on:** June 12, 2016, 12:32:59 PM »

Exploratory tear down begins: As of right now I'm down to flywheel removal...and nothing out of the ordinary has raised it's head.

gone_ape · « **Reply #47 on:** June 12, 2016, 12:42:46 PM »

All the transmission fasteners including the clutch pack allen screws were tight......
I sheephishly attempted to show in pics - one handed because of the phone cam - gently pushing, pulling, twisting, torqueing the clutch assy to see if I could reproduce "The Knock"...I could spin the engine a little both directions, but no end float, no tangs in tab slap, nothing............so, off with the flywheel...but the Texas heat is preventing me from working in the garage today (yesterday, tomorrow etc)

gone_ape · « **Reply #48 on:** June 12, 2016, 08:21:25 PM »

What I think Gryphon and Rhoades were trying to explain is diagrammed here.... the Output Shaft has "slots" which are engaged by the "tabs" on the Gear Wheel shown here which is inside the engine cases behind the flywheel. ...and by removing the flywheel, cleaning (by contact cleaner)
through the holes of the 'Gear Wheel' - reaching the slots in the output shaft - and then reinstalling the flywheel (with new nut, compression ring and o ring of course) and torquing the nut to the largest of the recommended BMW spec for the nut, the problem should be solved.....TBC....

kennybobby · « **Reply #49 on:** June 12, 2016, 09:34:39 PM »

Item #8 in the diagram is the anti-backlash spring, a source of noise in the K100's. The notch looks like a good candidate also.

The balance shaft is accessible thru the bottom of the brick, the oil sump area, which if you remove the cover may let you hear the clank better.

For sure the noise is not caused by dirt--that's the cleanest bike, clutch and workshop i've ever seen...

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Author Topic: 1989 K75 engine rattle/knock. (Read 181868 times)