Hi everyone.

I'm posting this problem under the 'Engine and transmision' forum because I'm guessing the problem must have its source somewhere there, but I honestly don't know.

For quite a few years now I’ve experienced a bad vibration in the right rear footpeg of my ‘91 K75RT . It appears in the 3000 RPM range and the 5000 RPM range, regardless of the bike being on the centre stand or on the road. This is the only place where the vibration is experienced. The vibration can be felt very slightly at the front end of the footrest mounting plate and it increases the further aft you go, becoming very bad at the footpeg.

It didn’t arrive insidiously over time. It was just suddenly there one day. I could ignore it as it doesn’t affect me as the rider, but it’s so bad that my wife’s right foot goes numb if I’m in those RPM bands long enough, and as we all know an unhappy wife is not a good thing!

The first thing I checked for was a possible crack in the footrest mounting plate and possible cracks in the frame. Nothing. I’ve had the fuel injector sync checked. It was Ok. Changed the rubber shocks in the alternator, loosened off and re-torqued the engine mounts (added a shim at the bellhousing mount) to ensure I wasn’t capturing a stress point in the frame. I’ve had the clutch apart while greasing splines to see if somehow the various components had been assembled out of balance (they are 120 degrees apart). The clutch friction plate shows absolutely no sign of wear, as do any of the other clutch components. In desperation I’ve even run it (on the centre stand) with the rear shock (Progressive) disconnected (sounds weird I know), and also made a brace for the rear footpeg mounting plate in the hopes of dampening the vibration. I’ve even tried wrapping padding around the footpeg, but it doesn't help. The last place I’ve looked (just last week) was under the timing chain cover, thinking that maybe the vibe was somehow coming from wear in there. Sounds desperate doesn’t it!

In short, I haven’t uncovered anything on the bike that could be the culprit. The engine runs smoothly and has plenty of power and is a joy to ride, except for this one problem. The nearest dealer told me that he could try to find the source but, given what I’ve already done he said it could be a very expensive proposition with no guarantee of success.

At the end of my tether. Any suggestions anyone?

K75's were always renowned for their smoothness so clearly something is out of kilter somewhere. It sounds as if you have carried out a pretty comprehensive examination to find the source of the problem (a wife will do that to you) and I am sorry to say that I cannot think of anything else that might help. However, I feel confident that somebody with greater knowledge than my own will be along shortly to point you in the right direction

plugs, valve adj?, I have k75 as well as k100, k75 is normally pure smooth. I did have a bad vib, after I did a spline lube once, it was the drive dampers in the alt. and you covered that.
maybe drive shaft ujoint
good luck

Thanks for the encouragement krambo. Yankeeone, definitely not the drive shaft u-joint as the vibe is there when it's in neutral and on the centre stand. The plugs are good (Bosch X5DC) and the valves are within, or on, specs. Think it might be worth re-shimming them to put them on the other end of specs?

P.S. Happy Easter

I'm no expert but have you tried getting your wife her own bike?
Cheers RT

I also have a K75 and it's vibration free contrary to the k100.
Your problem is really weird.
Do you have the 'Z' saddle bag bracket on your bike? Would it be transmitting the vibration to the back of the footrest mounting plate?
This may not be the source of the problem but just what is conducting the vibration to the foot peg (As and example, a set of wrenches vibrating in the seat cowl).

Any vibration on the exhaust heat shield? (common place for vibrations). Is the rubber where the stand rest on in good condition?

The mounting plate is attached to the gear box and the swing arm pivot is in the back of the plate. Have you checked the 3 6mm screws holding the pivot?

One stupid question... Are the screws holding the plate the right size and do you have the wave washers under their head?

Is the rear mudguard (plastic) tight? I've seen parts #4 and #14 rusted and broken.



CF

Our bikes do vibrate but usually its so pleasant that we dont consider them annoying, however when such a frequency appears it is often traced to the mountings. as you say its only the right hand rear footpeg that is amplifying the vibes. so look there again. take it off and put it back on taking care to ensure it touches on all three places evenly. bolt it up and clear any other items such as the reservoir or pannier frame etc. try it before adding anything else. Try adding a washer to each to pack it out. You said it appeared when on the centre stand also, so that eliminated the centrestand touching some part of or bolts on the panniers frames, that was my first thought. It also eliminates the exhaust on the centrestand. You have had it off once already so that eliminates a rock stuck in behind the master cylinder or footpeg mount. It should not just appear without a reason, have you had it serviced or something?? Did your favourite pillion notice it before or did it just appear all of a sudden. Have you dropped it?? Do you know if the engine mounts are sound you mentioned the three back ones.

what about the circlips on each end of the centre stand pivots ....if one went missing lately ...the geometry may have changed ......dont forget to grease up the pivot points as well ..

just a thought

RT wrote:I'm no expert but have you tried getting your wife her own bike?
Cheers RT

I tried a different approach to the problem. Several weeks ago I told her that I could resolve the whole thing by trading her in for the one-legged variety. No right foot, no problem.

My doctor says that given plenty of rest and proper treatment I should be out of my wheelchair before the end of the year.

Good feedback everyone. I’m starting to feel not so alone with this problem and I’m hoping for one of those ‘Eureka!’ moments.

C.F. ...........

I do have the ‘Z’ saddlebag bracket. I think there’s too much flex in the bracket itself to transmit such an intense vibration, but you never know. I’ll try disconnecting it to see if it helps. Heatshield is good. Rubber for the stand is good. The 3 swingarm pivot screws are in place and torqued. I’ve had them off a few times to do spline lubes. The plate mounting screws are the originals (no wave washers) and were in place for years before the vibe started. Mud guard brackets are as new.

K75cster ............

The bike has never been dropped. The problem started about seven years ago and as far as I recall it appeared a couple of months after doing a complete spline lube (fore and aft). It just appeared one day on a run. I’ve had the transmission out a couple of times since to lube the splines again and to try to find if I screwed up somewhere on reassembly. Doesn’t look like it ... at least to my eyes, but I might just be repeating something stupid. Following Haynes to the letter though. I’ll follow your advice on taking the plate off and checking to see if the mounts are touching evenly. I’m going to try centreing the engine in the frame again. The last time I did it the gas tank was on and it had a lot of gas in it. Could be that was a mistake as the weight might have affected things. I’ll take a really good look at the engine mounts while I’m at it.

Charlie99 .........

The centre stand circlips are still in place but I know there is some wear at the pivot points. Got to install grease nipples for more effective greasing.

you never saw it comming huh ?.........too funny mlr ....

Time to get a side car..
It will solve the problem for your wife and you will be able to ride with your broken leg.

The problem started about seven years ago and as far as I recall it appeared a couple of months after doing a complete spline lube (fore and aft).

Given it occurred after having the splines lubed, was it re-assembled in exactly the same place. These parts wear together, and now could be out of balance.

Mike

hmm .....good observation mike !!!

Mike, your idea is a good one. Re-aligning the splines in their original position is something I had never considered. That particular spline lube was the first one I had done and I gave all the splines a really close inspection and couldn't detect any wear on them. The lubes I've done since haven't shown any wear either. If what you say is possible, and I'm sure not ruling it out, do you think it could take a couple of months before an imbalance would show up?

I would have thought that it would have been felt immediately, but as lots of problems can be traced back to the last time some work was done, it's worth checking.

It could be just coincidence of course. Did you check the joints for wear when you were lubing the splines, maybe they were on their way out anyway?

Mike

Hi Mike

If it's the drive shaft joints you're referring to they don't come into play with this problem as the vibration in the footpeg is there when the bike is in neutral on the centre stand.

I know what you mean about problems being traced back to the last work done and it's something that's always in the back of my mind.

If it's the drive shaft joints you're referring to they don't come into play with this problem as the vibration in the footpeg is there when the bike is in neutral on the centre stand.

Sorry, you did mention that earlier - I will now stand in the corner for an hour and recite:

I must read the posts again before responding, I must read the posts again before responding...............

Mike

Not a problem Mike. I'm pleased with any and all responses on this thing.

And don't worry about having to stand in the corner. I've worn out many a corner in my life by having to stand in them too many times.

....... MLR

I know it's not finding the cause but how about fitting an early rubber mounted footrest plate? Desperate measures,but....
Paul.

MLR when your doing 3000 rpm have you chased it with your knee or foot on the motor or places like that. Bar end weights solve most issues with bars vibrating as they do for k100 owners and kwaka an honda owners for that matter. The vibes are there from something not balanced like maybe a piece of clutch plate fibre coming off or alternator boot possible failure. Have you done a clutch lube since this started or had you just finished one? It seems far more logical to chase the vibe than apply some bar end weight type solution to the offending peg although a borrowed r/h peg and mount would be a way of testing some of these ideas that have poped up. I dont get it though the frame dont touch the pegs so shimming it shouldn't make much difference. A silly suggestion I spose but have you tried using a long screw driver place the handle to your ear and the spade bit to different parts of the peg and motor gearbox bellhousing and see what happens

Have you changed the plate that holds the pegs. It is only 3 bolts and I am sure any K100 owner would help out with a try and see.
Metals are strange and injection moulded stuff even stranger, it could even have developed a resonance for those frequences. Injection moulded aluminium can even have or develop internal fractures.

All good thought guys.

Sidecar paul: the old rubber mounted one could be an option down the road. Thanx. One thing I had tried a few years back at the suggestion of an aircraft mechanic friend was to put rubber spacers between the mounting plate and the engine unit. It didn't make much difference and because I couldn't torque the mounting bolts properly without crushing the rubber I abandoned the idea. Didn't like the idea of the brake pedal being mounted on something not firm either.

K75cster: I had done a clutch lube a couple of months before and have done a couple more since (the second one just to see if I had screwed something up). Everything in there looks like it just came from the factory. I will do the screwdriver stethoscope thing as you suggest just to see. You never know.

Rick G: An interesting thought. I'm sure I could get my hands on another mounting plate somewhere and give that a try. No signs of cracks in what I have but your comments hold water.

Thanks guys. ..... MLR

+1 on the screwdriver stethescope it can really help to identify the type and location of the related vibration source ....(quietly ive been thinking the mufler damper on the other side is hardened up and is causing "sympathy" vibrations )

Charlie99, the muffler damper is something I've never considered. Poking at it with a scriber the rubber feels fairly resilient but that's just at the exposed end. Other than replacing it, any thoughts on testing it?

not sure mlr ...as i have an aftermaket exhaust ....(the way it came to me ...fortunatly ) i figure the stethescope will certainly help though ...twas a good idea k75

Thanks for the compliment charlie, unfortunatly I cant just jump on mine and test. As it seems i've developed dissassemblitis and I've got more bike bits than bike at the mo. maybe another can try sticking a peice of wood in between their 75's muffler and footpeg to see if they can invoke a vibe on the r/h footpeg? Meanwhile my disease appears only slight as the shed is mostly intact and the foundations of the bike are still sitting on the centrestand and a jack in the middle of the floor. chuckle.

I'm in much the same situation as you k75cster, but I don't think quite so 'advanced'. I was away for a month and a bit during the winter and my projects on the bike were delayed. The problem with starting winter projects in the Spring is that all the Spring projects come due as well. Spare time underload! I don't expect to get my bike out of the basement for at least another couple of weeks in order to fire it up and follow up on all these good suggestions.

I know! I know! I can hear it now. Set your priorities MLR (i.e the BIKE!)

I'm about to do a paint job on mine, Engine gearbox diff swingarm etc to make it all pretty for the raod again

Well I took my wife out for her first ride on the K today and she complained about the footrests vibrating, particularly the LEFT one. I told her that these bikes do vibrate a little up to around 3,500 rpm but smooth out nicely after that. No she said, it's giving me pins and needles . So while we're riding along I put my foot on her footpeg and bugga me it was really bad . Mine are as smooth as silk. The rest of the bike seems smooth to me, even the bars are ok. I've been searching the net for possible solutions so seeing as this thread didn't get a final result and it's pretty old now I was wondering if anything new has been found over the years in regards this problem.
  I'm going to start checking a few things suggested in this thread this afternoon. 

  Edit: Doesn't do it at idle  only when accelerating or at constant speed. 
          Does it when on centre stand also when I increase the revs.
          Right peg got worse when I took the panniers off.
          
  Cheers
  Andrew

I had been thinking about this for a while

Andrew ...have you undone the exhausts from the head ? 
I was thinking if there was some stress on the header pipes . that may contribute to the vibrations , along with an offset of the muffler to footpeg mounting plate

so likely needs new or re annealed copper washers that fit between the pipe and the exhaust flange - port , new would be best

mount up the exhaust very loosely , including the muffler section to the foot peg bracket and notice if there is any offset of the muffler to the hanger on the foot peg plate ...if there is, sometimes a washer under the rear mounts of the footpeg mounting plate can move the plate out so that you get a vertical drop rather than an in or out offset to the hanger  ...I have done this on the right hand side so that the panieer bracket clears the spring of the shock by more than a couple of mm ...and the left hand side when I saw that the hanger bracket was tight to the footpeg plate mount )

and do the nuts up on the exhaust so they just start to take up on the washers  , do them equally obviously

the main thing is not to overtighten any particular one of the exhaust headers , they only need to seal, not ram home and squish the copper washes to within a millimeter of thickness

the k75 has a shim around the exhaust  - muffler interface -join ..perhaps undo that as well till after its all mounted and tested for a seal to the head
the k100 has the flanges on the standard exhaust which shouldn't be done up till after the system is mounted and tightened up at the exhaust header and muffler mount , run the bike to check the exhaust is sealing on the pipes ...then tighten the flange clamps as the last thing

hope that helps  some ?

Thanks Charlie,
   I'll disconnect the muffler from the footpeg hanger first and see if the vibration gets any better. I'm just wondering how the muffler would be making the right side pillion peg vibrate though?. It did get worse on the right side when i removed the pannier also.

there would be some resonance left to right hand side  I guess Andrew ...the foot mounting plates are like wings with vibration coming in from the extremities ..and if pannier brackets fitted,  more ways to resonate the vibrations ..its not as if they have any weight to resist the vibrations eh?

Fair call.
Small update. 
   I went for a ride and used my foot metre to test for vibration. The muffler is vibrating bad when I place my boot on it ( or at least the shiels is ). The centrestand is vibrating bad when I push down on it. The footrest hanger is vibrating. The sidestand is NOT vibrating when I push down on it.

hmm perhaps try undoing the muffler hanger  and test again ?

hoping that the exhausts are all tensioned up similarly

Hello!

Just thinking, my problem was solved by motorcycle wheel balancing.
Could be the rear wheel.

Cheers

charlie99 wrote:hmm perhaps try undoing the muffler hanger  and test again ?

hoping that the exhausts are all tensioned up similarly

  I'll be trying that tomorrow morning for sure. I probably won't even have to go for a run as it does it on the centre stand. I'm heading out to check engine mount and header torque now. Looks like 30ft/lbs for the engine mounts and 11 ft/lbs for the headers.

Chocolate wrote:Hello!

Just thinking, my problem was solved by motorcycle wheel balancing.
Could be the rear wheel.

Cheers

 
  Hi Chocolate,
    I was wondering about that as I've just put a new rear tyre on but thought the whole bike would vibrate if it was out of balance and not just the rear footpegs. Actually the tyre guy did say something about the rear rim but I can't remember what it was now. I have noticed a "DRONING" in the motor of late but I'm not sure if it was always there and I'm only noticing it now that I'm riding it more??.

if headers have been over tensioned they could be out of alignment in any case  because they crush the seals pretty quickly

just a thought

charlie99 wrote:if headers have been over tensioned they could be out of alignment in any case  because they crush the seals pretty quickly

just a thought

  I just undid the 2 bolts that hold the muffler onto  ( the Z rack bolts actually ) the footpeg hanger and got the wife to sit on the bike while on it's centre stand while I revved the motor and the vibration in the left footpeg had gone. The right was worse. A proper test tomorrow when we go for a short ride. I'll cable tie the muffler so we don't lose anything. I also found half the heat shield bolts to be a bit on the loose side.
  So now that it's seems to be the muffler do I undo all the header bolts and re-tighten?.

charlie99 wrote:if headers have been over tensioned they could be out of alignment in any case  because they crush the seals pretty quickly

just a thought

  Charlie, 
   can the copper seals be bought at an automotive shop or are they a special size?.

  Cheers
  Andrew

Do you have the correct mounting bracket for the exhaust?

It's differen't length on the distance pieces where the screws go through,
depending on if Z-brackets is mounted or not.
If the mounting brackets for w/o Z-brackets is used together with the
Z-brackets, the silencer gonna be pushed sideways to the left right and be
under tension.

Or a bad modification, often these distance pieces is just cutted/grinded
to adjust the length.

Andrew2 wrote:

charlie99 wrote:if headers have been over tensioned they could be out of alignment in any case  because they crush the seals pretty quickly

just a thought

  Charlie, 
   can the copper seals be bought at an automotive shop or are they a special size?.

  Cheers
  Andrew

I haven't seen the right size copper ones locally mate

not saying they arent available , just haven't seen them

most bike exhaust flange seals iv seen were aluminium and some form of fibre ...(probably used to be asbestos I guess )

that's  interesting that the right side still vibrates ...hmmm

is the side stand down whilst doing this test ? or is it sitting on the exhaust stopper bracket ?  and shaking the centre stand mounts etc ?

hey inge ,  whats the exhaust seal size ?  don't have my list right now


and Merry Christmas whilst iv got your attention

charlie99 wrote:
hey inge ,  whats the exhaust seal size ?  don't have my list right now


and Merry Christmas whilst iv got your attention

32 x 40 mm

Inge K. wrote:Do you have the correct mounting bracket for the exhaust?

It's differen't length on the distance pieces where the screws go through,
depending on if Z-brackets is mounted or not.
If the mounting brackets for w/o Z-brackets is used together with the
Z-brackets, the silencer gonna be pushed sideways to the left and be
under tension.

Or a bad modification, often these distance pieces is just cutted/grinded
to adjust the length.

  Not sure if it's the right mounting bracket Inge. Here's the best photo I could get. It's not bolted on in these photos as I'm going to test the bike in the morning with it unbolted.

charlie99 wrote:

Andrew2 wrote:

charlie99 wrote:if headers have been over tensioned they could be out of alignment in any case  because they crush the seals pretty quickly

just a thought

  Charlie, 
   can the copper seals be bought at an automotive shop or are they a special size?.

  Cheers
  Andrew

I haven't seen the right size copper ones locally mate

not saying they arent available , just haven't seen them

most bike exhaust flange seals iv seen were aluminium and some form of fibre ...(probably used to be asbestos I guess )

that's  interesting that the right side still vibrates ...hmmm

is the side stand down whilst doing this test ? or is it sitting on the exhaust stopper bracket ?  and shaking the centre stand mounts etc ?

hey inge ,  whats the exhaust seal size ?  don't have my list right now


and Merry Christmas whilst iv got your attention

 I think it was up

Andrew2 wrote:  Not sure if it's the right mounting bracket Inge. Here's the best photo I could get. It's not bolted on in these photos

It looks like you have the wrong bracket, which is to be used w/o the Z-brackets.

Here is a photo of the one which is to be used together with the Z-brackets.

Inge K. wrote:

Andrew2 wrote:  Not sure if it's the right mounting bracket Inge. Here's the best photo I could get. It's not bolted on in these photos

It looks like you have the wrong bracket, which is to be used w/o the Z-brackets.

Here is a photo of the one which is to be used together with the Z-brackets.

 
  Do you have another angle of that Inge?.

It's from the net, mine is mounted on the bike.

Here is a picture of the one to be used w/o the Z-bracket, so you can see the difference:



The difference in length on the distance pieces is = thickness of the metal
sleeves inside the Z-brackets.

I see what you mean now. So the prongs on mine are too long causing the muffler sit at the wrong angle like what they are talking about in this thread.
https://www.motobrick.com/index.php?topic=8521.0

  They're saying to grind 5mm off the the longer prongs. Do you know how long the prongs are for the shorter version?. Just to be sure that I'm not cutting down the already short version .

  Cheers
  Andrew