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Author Topic: K75 doesn't seem as smooth as it should be  (Read 60849 times)

Offline ReneZ

  • ^ Motobrick Curious
  • Posts: 54
Re: K75 doesn't seem as smooth as it should be
« Reply #25 on: June 01, 2014, 10:23:14 AM »
Nice color scheme on the bike  :2thumbup:
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Greetings, Rene

BMW K100 - 1984
BMW K1200GT - 2003

Offline K75RT Keith

  • ^ Proficient Motobricker
  • Posts: 447
Re: K75 doesn't seem as smooth as it should be
« Reply #26 on: June 03, 2014, 03:31:15 PM »
Check the caps on the vacuum ports for cracks and think about checking the valve clearance.   Also the tires may be slightly out of balance or slightly cupped which could also be the cause for the vibration. 
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1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #27 on: June 03, 2014, 09:09:05 PM »
I'll get to checking the valves before too long.

But, if the vibration goes away when I pull the clutch and let the engine idle while traveling 80 mph, and the vibration goes away, how can it be the wheels or tires?

I haven't ridden for a straight hour yet (plan to tomorrow) but I haven't gone numb yet, so I think the issue has been solved. I still feel like a "hum" through the bars and all but that's normal, right?
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline Motorhobo

  • +25 years of K75
  • ^ Quintessential Motobricker
  • Posts: 1530
Re: K75 doesn't seem as smooth as it should be
« Reply #28 on: June 04, 2014, 12:27:45 AM »
I can't say I've even perceived any vibration thru the bars that I'd describe as a hum, I.e having a specific amplitude or frequency that differs from the vibration produced by the engine. The entire bike vibrates in concert with the engine...it doesn't feel like I'm taking any more vibration through the bars than anywhere else on the machine.

You didn't mention if you get it with the bike on the center stand throttled up to 5500 rpms on neutral.

Find a seasoned motobricker to ride it and tell you if it's normal. Except when they get back you might find that sweet fairing missing  :neener:
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1994/1995 K75 ABS Frankenbike: original engine 136k miles, frame from Gary Weaver (RIP), 173k miles -- Current Odometer: 198k miles
1994 K75 since 2013, 82,000 mi (19k mine) w/California Sidecar Friendship II Sidecar & Black Lab 'Miss B' - RIP

Past: 1974 Honda 550/4 (first bike), 1994 K75 (sold), 1995 K75 ABS (parts bike), Sidecar Dog & Best Bud 'Bo' - RIP

Offline K75RT Keith

  • ^ Proficient Motobricker
  • Posts: 447
Re: K75 doesn't seem as smooth as it should be
« Reply #29 on: June 04, 2014, 11:39:46 AM »
Just ride it to the National Rally in St Paul mn in July, There'll be a bunch of folks who know K75's and will gladly check it out for you.
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1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #30 on: June 04, 2014, 04:16:18 PM »
I'm thinking about it...the dealer (literally down the road from me) has a K75s...I don't want to waste their time or anything but I'd like to take that out and see what a K75 should feel like

Another thread I came across while Googling mentioned having the clutch assembly balanced by a machine shop, or at least having a machine shop figure out how they're supposed to be configured. I'm about to the point of having that done because after reconfiguring it the vibration seems to be better but still not like it's supposed to be.
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline K75RT Keith

  • ^ Proficient Motobricker
  • Posts: 447
Re: K75 doesn't seem as smooth as it should be
« Reply #31 on: June 04, 2014, 04:21:01 PM »
If it's BMW of G.R.  Go have a talk with them.  My experience with them when looking for a K75RT was better than most.
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You can't help someone who doesn't want to hear the answer.

1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #32 on: June 04, 2014, 05:18:07 PM »
Yup it is. I don't think I'm more than 2 miles from there. I've had some keys for my side cases on order (for like a month now) but I may be dropping in there Friday...I'll bring it up and see what they say. They have told me before that I'm welcome to test ride anything they have. Though I'm not buying another bike from them anytime soon I have ordered parts from them so I'm at least "in the system"...I dunno if that makes sense but
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline K75RT Keith

  • ^ Proficient Motobricker
  • Posts: 447
Re: K75 doesn't seem as smooth as it should be
« Reply #33 on: June 04, 2014, 10:21:23 PM »
They kind of work on the "old" style of sales.  Build rapport, let the customer try before they buy, offer assistance and advice, give the customer the opportunity to buy rather than sell them.  IIWM, I'd ask to ride theirs and explain what the symptoms I'm experiencing are and if someone who knows K75's might be able to give some advice or take mine a run and give me their honest assessment, at no charge of course.
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1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #34 on: June 05, 2014, 10:33:09 PM »
In the meantime I realized that when I put things back together there was a decent gap between the frame on the left side and the trans. I thread on ADV rider regarding a vibrating K75 mentioned this gap so I picked up a washer which fit perfectly with the bolt removed...retorqued the bolt and went for a ride but no change there.

If I end up stopping by the dealer tomorrow I'll see what they say
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 2308
Re: K75 doesn't seem as smooth as it should be
« Reply #35 on: June 06, 2014, 07:15:35 AM »
There is a specific tightening sequence for the frame bolts on the K75, and it involves putting shims only behind the frame bolt that mates with the top of the bell housing (Bolt #3).  You shouldn't shim Bolt #4.  The proper tightening sequence is on page 8.87 of the BMW technical manual.
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  • Regards, Robert
Toronto, Ontario

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

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #36 on: June 06, 2014, 09:33:53 AM »
will check the manual and go through the sequence this weekend
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline TimTyler

  • Adrninistrator
  • ^ Quintessential Motobricker
  • Posts: 1884
Re: K75 doesn't seem as smooth as it should be
« Reply #37 on: June 06, 2014, 10:56:39 AM »
Quote from: rbm on June 06, 2014, 07:15:35 AM
... on page 8.87 of the BMW technical manual

I think "8.87" is the manual's print date.

Try page 11.97.0 of the 8.87 tech manual.

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Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 2308
Re: K75 doesn't seem as smooth as it should be
« Reply #38 on: June 06, 2014, 11:32:50 AM »
Oops, I had quickly looked at the bottom of the page and assumed the first number I saw was the page.
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  • Regards, Robert
Toronto, Ontario

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

Offline Motorhobo

  • +25 years of K75
  • ^ Quintessential Motobricker
  • Posts: 1530
Re: K75 doesn't seem as smooth as it should be
« Reply #39 on: June 07, 2014, 01:53:01 PM »
 I got a chance to run my brick at +90mph/+6000rpm today -- smooth as silk. At 78-89mph/5500-6000rpm -- not so smooth. Up to 75mph/5000rpm -- smooth. That's just me -- don't know if all K75s have this behavior, but my bike seems to like high and low rpms, isn't so happy in the 5000s.
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1994/1995 K75 ABS Frankenbike: original engine 136k miles, frame from Gary Weaver (RIP), 173k miles -- Current Odometer: 198k miles
1994 K75 since 2013, 82,000 mi (19k mine) w/California Sidecar Friendship II Sidecar & Black Lab 'Miss B' - RIP

Past: 1974 Honda 550/4 (first bike), 1994 K75 (sold), 1995 K75 ABS (parts bike), Sidecar Dog & Best Bud 'Bo' - RIP

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #40 on: June 07, 2014, 09:08:04 PM »
How does this happen with something designed on the Autobahn, for the Autobahn?

I didn't get a call from the dealer about my keys tomorrow nor today, so I didn't get to stop in to see what they might have to say about my issue and taking their K75S for a spin. Will try to next week though
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline Motorhobo

  • +25 years of K75
  • ^ Quintessential Motobricker
  • Posts: 1530
Re: K75 doesn't seem as smooth as it should be
« Reply #41 on: June 08, 2014, 09:00:33 AM »
90+ is flow of traffic on the Autobahn...at least it was back in the 80s when I was driving on it regularly. At 80mph you just hang out in the slow lane. So maybe the Kbike is designed for that. Not saying my brick was shaking or vibrating abnormally at 85, just sayin it seemed smoother at 90.

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1994/1995 K75 ABS Frankenbike: original engine 136k miles, frame from Gary Weaver (RIP), 173k miles -- Current Odometer: 198k miles
1994 K75 since 2013, 82,000 mi (19k mine) w/California Sidecar Friendship II Sidecar & Black Lab 'Miss B' - RIP

Past: 1974 Honda 550/4 (first bike), 1994 K75 (sold), 1995 K75 ABS (parts bike), Sidecar Dog & Best Bud 'Bo' - RIP

Offline K75RT Keith

  • ^ Proficient Motobricker
  • Posts: 447
Re: K75 doesn't seem as smooth as it should be
« Reply #42 on: June 08, 2014, 05:53:29 PM »
Depending on how fanatical you want to be, you could:

Pull the crank, cams, transmission shafts and driveshaft and have them straightened to below the TIR spec.
Weigh each piston assembly and grind off the casting/forging marks until they are as close to the same weight as possible. (a trick we used on VW dragster motors)
Replace all the bearings and bushings to ensure that none are worn resulting in vibration.


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1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #43 on: June 08, 2014, 08:01:48 PM »
I suppose blueprinting the engine would be a for-sure way of doing it, but getting it to be like how it was from the factory would be nice (counting that this amount of vibration is abnormal). I'm thinking that in the next few weeks I'll tear it apart again and have a machine shop spin all the components and I'll replace the clutch disc as well
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #44 on: June 20, 2014, 07:24:05 PM »
Dropped by the dealer and picked up a new clutch disc this afternoon. I intend on installing it tomorrow afternoon.

The parts counter dude seemed to be pretty "tight lipped" when I mentioned assembly of the clutch components and markings, but I went in the service department door before leaving and talked with the service manager...

He said to line up the factory marks...which is NOT what the clymer manual suggests.

I'll see what I can figure out tomorrow.
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline Inge K.

  • ^ Quintessential Motobricker
  • Posts: 1451
Re: K75 doesn't seem as smooth as it should be
« Reply #45 on: June 20, 2014, 07:45:44 PM »
Quote from: F14CRAZY on June 20, 2014, 07:24:05 PM
He said to line up the factory marks...which is NOT what the clymer manual suggests.

From the factory manual...print out...show to the service manager...don't forget to slam the door.


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Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #46 on: June 22, 2014, 12:19:59 AM »
I'd like the motobrick community to know that I don't trust vehicle repairs or maintenance to ANYONE, except when it comes to things that are not practical (such as aligning all 4 wheels on my Subaru)...

At any rate, I had the clutch out again today to replace the disc due to its splines that were nearly used up. From an idea mentioned somewhere, I tried re-orienting the components and setting them on a tennis ball on a table then spinning the assembly (minus the disc and diaphragm spring) to figure out what position everything was balanced in. I found I could make it better but didn't get a conclusive result.

I picked up a "portable wheel balancer from Harbor Freight to see how it would work with the assembly (one of these):



Without getting into its effectiveness as a wheel balancer, which seems to be of debate if you search for reviews of it, I couldn't get the assembly situated on the balancer right due to the hole in the clutch cover being smaller than the cone-type thing on the balancer which wheels would be centered on. Also, it wasn't heavy enough to press down the spring loaded thang. I'll take the thing back tomorrow.

Except for the orange-ish paint on the clutch cover I truly can't find any decent paint marks on the components to set them 120 degrees from each other (which I believe is the correct way to do it, regardless of the advice of my dealer's service manager). It doesn't help that someone added paint marks on the pressure plate-type thing. Using the tennis ball method (hey it was the best idea I've come across) I got the assembly oriented with what seems to be the best balance and threw everything back together. I'll test ride it tomorrow after adjusting the clutch.

BTW, could this have been causing my vibration issue? I believe it went away since replacing the disc (will know for sure tomorrow):

Post


If the vibration seems to still be present I'll arrange to have a machine shop balance the damn thing
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline Elipten

  • ^ SuperNatural Motobricker
  • Posts: 715
Re: K75 doesn't seem as smooth as it should be
« Reply #47 on: June 22, 2014, 12:34:12 AM »
I suspect this balanced clutch pack and marks is a way out of date concept I the Kbike community.  There were no marks on mine when I took it apart in Jan.  and BMW techs and parts techs have told me the same.  How else could BMW sell you the parts separately?
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  • San Antonio, TX
  • 1990 K75RT

Offline F14CRAZY

  • ^ Quintessential Motobricker
  • Posts: 1091
Re: K75 doesn't seem as smooth as it should be
« Reply #48 on: June 22, 2014, 12:54:33 AM »
That's what I've wondered too
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  • Grand Rapids, MI
  • '87 K75C
'87 K75C w/ Pichler V1 fairing. LED's, CATZ driving lights, Audiovox cruise, LT top case, tons of other mods by Drake...

Offline Inge K.

  • ^ Quintessential Motobricker
  • Posts: 1451
Re: K75 doesn't seem as smooth as it should be
« Reply #49 on: June 22, 2014, 05:48:44 AM »
Quote from: Elipten on June 22, 2014, 12:34:12 AM
How else could BMW sell you the parts separately?

Each part is marked at its heaviest point, thats why they should be mounted 120o apart.
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