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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: andrej_gr on July 28, 2019, 12:59:49 AM

Title: K75 rattle
Post by: andrej_gr on July 28, 2019, 12:59:49 AM

I've got this periodical rattle sound on my 1995 K75. Seems to be coming from alternator area. Pulled clutch doesn't change anything. Can't hear it on higher rpm, but that might be due to engine sound becoming louder. Ideas?

https://www.youtube.com/watch?v=i4xJqmm5D6I

Title: Re: K75 rattle
Post by: Martin on July 28, 2019, 01:17:22 AM

More than likely the monkey nuts in the alternator. Use a stethoscope or alternatively a long screwdriver to confirm the source of the noise. Place the blade end of the screwdriver onto the engine and an ear on the handle then move it around until the noise is at it's loudest.
Regards Martin.

Title: Re: K75 rattle
Post by: The Mighty Gryphon on July 28, 2019, 11:59:30 AM

Rattle between 1200 and 2000 rpm is loose fit between output gear and balance shaft.  Nothing you can do about it.     

Title: Re: K75 rattle
Post by: Laitch on July 28, 2019, 12:57:19 PM

Quote from: andrej_gr on July 28, 2019, 12:59:49 AM

I've got this periodical rattle sound on my 1995 K75.  Ideas?

Sonic Defenders (https://www.surefire.com/tactical-equipment/earpro-products.html).

Title: Re: K75 rattle
Post by: K1300S on July 28, 2019, 03:01:17 PM

what gryph said.....if it goes away at idle and above 2k rpm.

one of my K75S's does it, the other does not.
https://youtu.be/q-3Ewx5VkYM

Title: Re: K75 rattle
Post by: stokester on July 28, 2019, 04:50:59 PM

Quote from: mlytle on July 28, 2019, 03:01:17 PM

what gryph said.....if it goes away at idle and above 2k rpm.

one of my K75S's does it, the other does not.

Ditto:
My '93 has no rattle, the '94 rattles like hell at low RPM until warmup.

Title: Re: K75 rattle
Post by: The Mighty Gryphon on July 28, 2019, 09:28:47 PM

I've had some luck with carefully adjusting the valves to the same clearance, cleaning the injectors with Techron, and adjusting the throttle body balance.  Makes it better, but it's still there.

I did have some temporary relief for a year or so by tightening the clutch nut on the output shaft after cleaning all the oil off the face where the balancer contacts it.  The trouble is that you need to take the clutch apart to get at it, so it's not something you want to do every year or so. 

The sloppy fit between the parts seems to have been built in.  When I had my engine apart I inspected the parts and the fit very carefully, and the gap is not the result of any wear, the parts were machined to fit like that.  I thought about tightening the fit by welding some additional metal, but held off due to not knowing how I would be affecting the hardness of the parts.

It's just something you have to live with.  It's a harmless part of the K75 engine's charm.

Title: Re: K75 rattle
Post by: Laitch on July 28, 2019, 09:36:09 PM

It sounds like a cat purring in its sleep. Don't disturb it.

Title: Re: K75 rattle
Post by: andrej_gr on July 28, 2019, 11:07:20 PM

So as per Martin's advice took off the alternator... Bingo!
 [ Invalid Attachment ]

Title: Re: K75 rattle
Post by: Laitch on July 28, 2019, 11:15:31 PM

(https://illiweb.com/fa/i/smiles/icon_cheers.png)

Title: Re: K75 rattle
Post by: Martin on July 29, 2019, 12:29:35 AM

Good result.
Regards Martin.

Title: K75 output shaft end play
Post by: aussiebeemer on April 25, 2020, 12:43:17 AM

HI K75s Vin WB1056306P0213381 I am replacing the rear engine output seal but notice there is 3+mm of endplay on the output/balancer shaft? (The shaft is disconnected from the clutch assembly)

Title: Re: K75 rattle
Post by: aussiebeemer on April 25, 2020, 04:25:36 AM

attached video of shaft movement [ Invalid Attachment ]

Title: Re: K75 rattle
Post by: daveson on April 25, 2020, 06:34:33 PM

That's a huge amount of endplay, but that's normal with the clutch nut removed.

Title: Re: K75 rattle
Post by: aussiebeemer on April 25, 2020, 07:29:26 PM

 112350 Happy to read that. thanks.

Title: Re: K75 rattle
Post by: Martin on April 27, 2020, 08:12:10 PM

I'm still running on a lot of my original parts including 170,000 KM monkey nuts. I've had spare nuts and cup in my spares inventory for years awaiting the dreaded sound of my nuts disintegrating. 44271
Regards Martin.

Title: Re: K75 rattle
Post by: aussiebeemer on April 28, 2020, 03:54:36 AM

Thanks for the info. I am giving the 75s a big freshen up after me being off the road for several years. My talented brother has repainted all body parts. Photo to come.