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Author Topic: K75 Engine noise  (Read 54752 times)

Offline bgcameron

  • ^ Motobrick Curious
  • Posts: 68
Re: K75 Engine noise
« Reply #75 on: April 25, 2021, 08:25:09 AM »
Quote from: daveson on April 25, 2021, 06:09:05 AM
So no light switch but km cluster? Dunno if that's normal for Canadica. How's about photos.

What maintenance history do you know of?
Some internet sleuthing revealed some maintenance history! See the article about splines. Hopefully this link works. If not, I will try to fix it later when I am not posting from my phone.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://static1.1.sqspcdn.com/static/f/760327/10120680/1294422490340/Beemer-Reader-17-09-September-2007.pdf%3Ftoken%3DmUfDhk4UT6LaBs50vL3N690JJFQ%253D&ved=2ahUKEwjV96nysJnwAhWyPH0KHWRFDQQQFjABegQIDhAC&usg=AOvVaw2SZu79ToCsVdlJfSTOSxyh
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  • Vancouver Island
  • 1990 K75S

Offline The Mighty Gryphon

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  • Posts: 6843
Re: K75 Engine noise
« Reply #76 on: April 25, 2021, 08:45:37 AM »
Is this article by the guy who owned the bike before you?  Here is what splines that get a light coat of HondaMoly 60 every 10,000 miles look like at 98,000 miles(160,000km). 


* DSCN3341.JPG (22.8 kB . 609x576 - viewed 597 times)

* DSCN3349.JPG (38.13 kB . 618x576 - viewed 599 times)

If your splines are okay, and they should be after a mere 53,000km, then throw a little lube on them and ride the damn bike.

When you put the drive shaft back in after you do the lube, make sure it's locked into the transmission output shaft.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline bgcameron

  • ^ Motobrick Curious
  • Posts: 68
Re: K75 Engine noise
« Reply #77 on: April 25, 2021, 10:49:40 AM »
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  • Vancouver Island
  • 1990 K75S

Offline The Mighty Gryphon

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  • Posts: 6843
Re: K75 Engine noise
« Reply #78 on: April 25, 2021, 12:00:48 PM »
My advice is to sell it to me.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Laitch

  • Faster than a speeding pullet
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  • Posts: 11299
Re: K75 Engine noise
« Reply #79 on: April 25, 2021, 12:08:07 PM »
You've got a gen-u-ine BMW comfort seat there, bg. They aren't common but get much better reviews for long distance riding than the OEM bench seats.  112350
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline daveson

  • ^ Quintessential Motobricker
  • Posts: 1268
Re: K75 Engine noise
« Reply #80 on: April 25, 2021, 05:24:40 PM »
That's absabloodylutely spotless, I should have known.

How's about the instrument cluster.

Hopefully, as has been said, just needs the cobwebs shaken out of it.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

  • ^ Motobrick Curious
  • Posts: 68
Re: K75 Engine noise
« Reply #81 on: April 25, 2021, 05:54:16 PM »
Quote from: daveson on April 25, 2021, 05:24:40 PM
That's absabloodylutely spotless, I should have known.

How's about the instrument cluster.

Hopefully, as has been said, just needs the cobwebs shaken out of it.



Quote from: Laitch on April 25, 2021, 12:08:07 PM
You've got a gen-u-ine BMW comfort seat there, bg. They aren't common but get much better reviews for long distance riding than the OEM bench seats.  112350

It's actually a reupholstered Corbin. It looks very similar to the comfort seat.
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  • Vancouver Island
  • 1990 K75S

Offline Laitch

  • Faster than a speeding pullet
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Re: K75 Engine noise
« Reply #82 on: April 25, 2021, 06:13:06 PM »
Quote from: bgcameron on April 25, 2021, 05:54:16 PM
It's actually a reupholstered Corbin.
:nono2: We'll need to see its papers. If it was a Corbin, it wasn't reupholstered; it was stuffed.  :laughing4-giggles:
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline daveson

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  • Posts: 1268
Re: K75 Engine noise
« Reply #83 on: April 25, 2021, 06:42:40 PM »
All good.

Since you don't have many posts, l looked at them for photos without luck, but noticed at least one valve out of spec. Over max for exhaust, surprising, dunno if you fixed it.

Anyways, it wants a full service and a lot of Kay's.

If you still have the noise, could it be something stupid like a loose air box vibrating? I was chasing a knock in the back of my car once, eventually, eventually I fixed it after emptying the crap out of the trunk. Then repacked it.

Another thing, the annular spring has been under compression for thirty years, regardless of the mileage, it may have lost some tension by now, with the result of a rattly idler gear. Big deal, you don't need an idle gear, you could throw it in the bin (it's only there to reduce noise, if rattly only increases noise.)
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

  • ^ Motobrick Curious
  • Posts: 68
Re: K75 Engine noise
« Reply #84 on: April 25, 2021, 07:08:26 PM »
I replaced 2 shims to bring it into spec. One was a hair tight and one was a little loose. I was thinking there might be something loose inside the airbox so I went through it and couldn't find anything.

I've been in touch with a local gentleman who has been riding a K75 since he bought it new in the mid 90's. He's offered some guidance on servicing and thought that the clutch splines are worth looking at.

Is the rattling idle gear the one that tends to make a bit of a zipper type of sound with abrupt revs from idle?

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  • Vancouver Island
  • 1990 K75S

Offline daveson

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Re: K75 Engine noise
« Reply #85 on: April 26, 2021, 12:22:40 AM »
Dunno.

How's about a video.

I spose the air box idea was wishful thinking on my part, I forgot the handlebar vibrating symptom.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

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Re: K75 Engine noise
« Reply #86 on: April 26, 2021, 12:49:13 AM »
Found some good info in here: https://www.k100-forum.com/t10397-engine-clatter

It may be a matter of simply retorquing a the clutch housing retaining nut.
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  • Vancouver Island
  • 1990 K75S

Offline daveson

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Re: K75 Engine noise
« Reply #87 on: April 26, 2021, 06:27:16 AM »
That's why I asked if pressure on the clutch changes the sound, but it didn't, making me back away from the idea.

So probably not a good idea to turf the idle gear in the bin, I forgot about its oil gallery, not that it'll come to that anyway.

What an incredible example of attention to detail by BMW, this oil gallery is. It can only rotate a small amount on its shaft, between two teeth of the driven gear.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

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  • Posts: 68
Re: K75 Engine noise
« Reply #88 on: April 26, 2021, 06:39:54 AM »
Quote from: daveson on April 26, 2021, 06:27:16 AM
That's why I asked if pressure on the clutch changes the sound, but it didn't, making me back away from the idea.

So probably not a good idea to turf the idle gear in the bin,  I forgot about its oil gallery.

Perhaps there is still slight contact between the clutch plates that is enough to agitate that gear in the balance shaft. Regardless, I should do a full spline service anyways and torque that nut while I am in there.
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  • Vancouver Island
  • 1990 K75S

Offline daveson

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Re: K75 Engine noise
« Reply #89 on: April 26, 2021, 07:27:13 AM »
Yep if the clutch nut turns with your torque wrench at its setting, its been loose.

While you're there,  check that the balance marks are in the right place. There was a thread where an unbalanced clutch caused a noise, but not vibration, surprisingly, maybe since the output/balance shaft turns in the opposite direction to the crankshaft.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline daveson

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Re: K75 Engine noise
« Reply #90 on: April 27, 2021, 11:04:43 PM »
OK another guess is that reduced tension in the circlip (or it's opened a little) could result in your symptoms, with the result of endfloat on the driven gear and maybe a bit of slop with the idler gear, but only under light load, so while coasting the spring load might be sufficient.

I've added more reasons to your link above.

I think with the crank cover removed you have a small window of access to the driven gear. Probably only useful to check for slop between the drive gear and driven gear pointing to reduced tension from the annular gear. Unlikely, but easy to check for. If there was any endfloat with the key off, you'd think the noise would be at all rpm ranges.

Please chime in if you think this is crap, it could well be, I don't want to waste anyone's time.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline daveson

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Re: K75 Engine noise
« Reply #91 on: April 28, 2021, 03:13:47 AM »
How the parts interact, this drawing is a k100, but the gears and circlip arrangement is similar. Not exact or to scale, just to help understand it.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

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  • Posts: 68
Re: K75 Engine noise
« Reply #92 on: April 29, 2021, 04:48:56 PM »
I showed the sound clip to the local BMW expert. He thinks it's the starter clutch. Will start disassembly soon.
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  • Vancouver Island
  • 1990 K75S

Offline daveson

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Re: K75 Engine noise
« Reply #93 on: April 29, 2021, 04:55:27 PM »
Are you going to open the starter?

Unfortunately there's no clutch in the starter.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline rbm

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  • Posts: 2308
Re: K75 Engine noise
« Reply #94 on: April 29, 2021, 05:07:05 PM »
I think he's talking about the spray clutch in the intermediate housing.
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  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline daveson

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Re: K75 Engine noise
« Reply #95 on: April 29, 2021, 05:17:33 PM »
True.  I was wondering if the BMW workshop is going to disassemble soon or bg is going to open the starter soon, or something else.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline bgcameron

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  • Posts: 68
Re: K75 Engine noise
« Reply #96 on: April 29, 2021, 08:11:10 PM »
Well, I am hoping to do the work myself. Has anyone here checked this component? It seems like the common issue with it is a no-start condition, but I have not read anything about it making noise.
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  • Vancouver Island
  • 1990 K75S

Offline daveson

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Re: K75 Engine noise
« Reply #97 on: April 29, 2021, 08:59:41 PM »
What work are you planning on doing? Opening the engine? That's a big job. I'd do some tests first to confirm it's the problem before doing that. Has the starter been working normally, does it sometimes slip? The crank could release the clutch, hard to imagine it could engage it.

If he means the starter is turning the clutch, I'd remove power to it (and insulate) and see if the noise disappears.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Laitch

  • Faster than a speeding pullet
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Re: K75 Engine noise
« Reply #98 on: April 29, 2021, 09:13:25 PM »
Quote from: bgcameron on April 29, 2021, 04:48:56 PM
He thinks it's the starter clutch.
:popcorm
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline daveson

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  • Posts: 1268
Re: K75 Engine noise
« Reply #99 on: April 29, 2021, 09:26:53 PM »
Dunno if it's been mentioned yet but removing the alternator might have an effect on the noise.
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  • Victoria, Australia
  • Current; '85 K100RT~100,000km; four other bricks. Past; Vulcan 1500, V Star 650, KLX 250(dirt bike) TT250(dirt bike)
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