hey guys,

i am sdorry that i ask more than help the others but i am still pretty fresh in the K bike thing;)

i've noticed those weid sounds some time ago but thought that that's how the K engine works like. now the thing is becoming more and more hearalbe so i started to worry a bit more.

it goes like this:

in the morning, when the engine is completely cold and i rev it up to let's say 3,500-4000 rpm a very loud rattling can be heard (like a stone in the engine) coming i would say from the engine/gearbox area but it's so vibrative and loud that it's actually hard to say. also, when i rev it and close the throttle, letting the bike brake with the engine, the sound is heard. after a minute or two of riding the sound disapears...

any ideas?

i am getting ready to change the breather, rubbers (between throttle bodies and airbox), clutch cable and a couple more things so maybe i could have a look at this one as well but i have to have an idea of what can it be.

thanks a lot for any help!

hmm hard to say paj ......but maybe the rubbers between the altenator and drive flange could be the issue ....they are a common issue for noise comming from what apears to be the engine...gearbox



there have been a few posts on this in the past i think there is even a tutorial somewhere ....



in a nut shell ....the altenator connects to the bell housing with a flange that has rubber insulators to the gear drive from the bell housing ....if these were defective ...broken ...what ever, you may well hear what you have described .



they dont cost much to replace (new parts ) just time and effort

yupp , thats the cush drive rubbers you speak of mate, like in a hub. it'd sound like a rock in a blender without them , prob leading to a failure .

hmm, but how to explain the temperature issue? the noise disappears after 2-3 mins from start

after starting the bike, the load on the altenator is more or less at maximum untill it recharges the battery ,

this may take several minutes

seems logical;) thanks a bunch, i'll look at that when i will be working on the other stuff next weekend. or should i fix it asap?

Have a listen with a screwdriver to see where on the engine it is coming from.
Regards,
K-BIKE

My guess is on the camshaft drive chain tensioner....

ok, i guess i can try to describe the sound a bit more in detail.

when reving on neutral, when i close the throttle it sounds like a dry, loose bearing falling into resonance - do you know what i mean ? it's like i used to play plastic toys and spin something very fast, ie using a small electric engine and then, at some speed the thing would fall into resonance and make a horrible rattle/squeak.

secondly, for me the sound comes from the gearbox/engine area, not from the camshaft area. it got louder when the temperature started falling close to zero here.

my guess would be something in the gearbox not getting enough oil at the beginning (those gearboxes are not pressure lubricated right?)

just a guess...
cheers

Paj does the noise disappear if you pull the clutch in?? could be dry thrust bearing or dry alternator bearings ?

our mate ably found a worn out intermediate gear bearing....to the alternator drive ....the other day .....hmmmm

i know i have a similar noise as well not quite as bad as yours paj .

im hoping and praying its the alternator drive bearing .....but a real pain to get to ,,,,i guess i need a handfull of bits once i plan to open the old bird up .....JUST hoping and praying its not the output shaft rivets

yeah, i was thinking about those rivets too mate... but honestly, is it really so hard to fix that? you just gave to remove the whole engine, tear the whole belly apart, replace the rivets and you're done

the alternator bearing also needs the gearbox out right? like i said, i will be working on it soon so i 'll check everything what is possible to check.

thanks!

Paj its not just replace the rivets because by the time the noise is evident the holes for the rivets are elongated
the alternator is easy fix take off cover left hand side 2 screwa then 3 screws to remove alternator

sometimes i wonder why am i trying to keep this old motorcycle alive instead of buying myself a new one... but i guess that's the way my life goes, i am addicted and happy to see that old K running like "new" haha.

i know that taking the alternator off is quite easy but changing the bearing (the one in the block) needs taking it all apart i guess.

about the rivets - is it something every K owner has to go through? my bike has 93kkm on the clock - does that mean i am close?

being an 89 model you should have a 12 rivet output shaft so no problem
and yes gearbox has to be out to do the drive bearing inside but whilst there you can clean the starter clutch

quick test take the alternator out then run the bike hopefully noise goes then its just bearings in alternator

aye ! toto... i think you might be able to discount that paj ...

discount meaning i may be free from that disease?

I hope I can be of some help on this, but I feel I may be the bearer of (more expensive) news.

1. Remove the alternator and run the engine to prove it is/is not an alternator problem.

2. Year model '89 is no gaurantee of 12 rivet output shaft. I had an '89 engine from a K100LT and it was 6 rivets. This can be seen by removing the RH side crancase cover.

3. Search the forum for my previous posts (Dennis) and you will read that it (the dry rattleing noise especially on deceleration when cold) is likely to be loss of tension on the backlash eliminator gear on the output shaft. This is caused by elongation of the hole that the spring tab fits in thus the gear tooth offset tension is lost. When the engine warms up it temds to get quirter, I suspect from slight expansion due to thermal growth. Look through Bert's restoration project, he has pics showing the worn hole in the output shaft assembly. You may also have loose rivets, especially if it's an ex police bike, they gave them a constant thrashing through the gears and it seems this added to the onset of the problem. Hope this helps, Dennis.

oh sh*t...

1. i will do so with a pale face and shaking hands, if that won't change anything:

2. i won't check it now

3. it's exaclty a dry, rattleing noise, mostly on deceleration when cold...

my bike is not a police bike (luckily) and it was imported from switzerland where it was electronically limited to 6000rpm so the engine shouldn't be THAT tired.

now a short question to make things clear - i am not 100% sure what does this damn output shaft do - does it transfer the whole engine power to the gearbox or what? my gears started working harder lately, they are more noisy and sometimes i have problems with putting the first gear in. but with this i am guessing it may be caused by an old clutch cable - i can not regulate it anymore and the freeplay at the clutch arm is around 100-110mm instead of 75mm (i got a new cable and will change it when i get to those damn rubbers as the cable goes though all the intestines of this bike).

saying that, does that mean i will have to tear that whole damn engine apart to get to those elements?

i will try to find the post you're talking about and i think i might have seen it before (a pic with a whole which should be round but it's eliptical...)

thanks, i'll try to check the thing with the alternator tomorrow morning...

PS Bert's restoration project... where and how can i find it? there's no user with a nickname bert;)

Bert is none other than our estemed leader Crazy Frog

i would be grateful for any suggestion where i can find that thread of his - i can't find it;)

i found a lot about 6 vs 12 rivet versions of the output shaft and...

i read that there were two types of bearings - the smaller one for the 6 rivet version and the bigger one for a new 12 rivet version (i guess).

basing on the OEM i have the bigger bearing but - it does not change from 1986 to 1991 so... i am cofusd.

is it really enough just to remove the right hand cover to see those damn rivets? will i loose a lot of oil?

cheers!

Sorry Pajonk, but I can't see Bert's restoration thread on the site anymore, I think there used to be a link to it on the home page. Bert will post it I'm sure if he reads this. You need to see the pics of the output shaft assembly and the worn spring locating hole. As for the output shaft and its purpose, it performs a few functions - it is connected to the crankshaft by an equal sized gear and it counter-rotates to balance out the reactive forces of the crankshaft assembly thus preventing the bike lurching sideways. The output shaft is connected to the clutch. The other (front) end of the output shaft drives the oil and water pumps and on a K75 it anlo serves as a balance shaft (it is weighted and timed). The backlash eliminator on the helical gear serves to provide silent operation of the gear drive. To see a similar arrangement on a car engine look at a Toyota Corolla 4A FE engine with 1 cam driving the other by gear connection. Look inside the oil filler cap and you wil see the thick and thin gears together, same system. On the negative side, yes the engine needs to be out of the bike (frame off the engine) to access the output shaft, though some have managed to remove it by holding the engine with straps etc while accessing the shaft assembly. Difficult but possible.

eh... those things are expensive! so first i need to take the RH cover off to see if the rivets are on their place right? but i am almost sure that that's the thing - the sound is hearable when decelerating on a cold engine and it rattles like hell! if i had a garage i wouldn't worry but in my situation and winter coming...

Here is the picture Dennis refers to:



Bert`s page you find at the Portal (K100 rt rebuild page).

The 12 rivet shaft came first on the RS 16V model, later on in the same year (-89) on the other models (somewhere during second half).

I also have loose rivets on my oldest K (for several years, but not much used lately) and have the
knocking sound at cold engine / low outside temp. (I just raise the revs at idle when cold).
But the rest of the sound description (dry bearing, resonance) I ain`t got.

It could be that you might have to separate problems.

Inge K.

yeah, i found it... they started putting 12 rivet shafts in 08.1989, mine is 02.1989...

and yeah, you're right, it might be two separate problems...i'll have to inspect it all first.

if i want to take the RH cover off, can i use the same seal like on the valve side?

Remove RHS lower fairing, all screws from the cover and swing it out in the rear end, place whatever is useful between the cover and engine block to keep the cover in position so you can see the rivets.

Put the bike in gear (on center stand) move the rear wheel forth and back while observing the rivets.

I did reuse the old gasket, just put a small amount of sealant compound at the aluminuim joints at
front and rear end.

Inge K.

I have found that if the rubber gasgets are a bit hard, soak them in petrol for about 10 minutes it will soften them a bit and help them seal.

Also I had a cam cover gasget shrink after it was off for a few days and soaking in petrol for about an hour worked for that and made it easier to fit.

it was close to zero in the morning so i decided not to work on the alternator and when i get back from work around 5PM it already starts to get dark so i guess i will have to wait for the weekend to come.

what i did was a test i read about in one of the posts regarding the output shaft - after starting the engine the knocking is pretty loud so i put the first gear in, git the rear brake and started letting the clutch go - the knocking disapeared what i understand means that my rivets are 90% busted...

second thing is that the dry, vibrative, rattling sound is getting worse every day i guess (only when engine cold) and today, when i tried to decelerate from around 4000rpm the noise was just super loud and vibrative...like an old, dry bearing. does that mean, basing on previous replies in this post, that i have my rivets busted and the spring, which you can see here on the picture?

cheers!

certainly worth investigation paj ....but dont give up mate ....there are ways of doing things ....and throwing money at the problem wont solve a missed diagnosis .

if you carefully check and test things in the appropriate way you may well be able to discount many others .....but mechanical wear is hard to get over without replacing the components .



if you decide to sell the bike ...i already know what to expect and will find it all really easy ....you arent far off getting the bike back to factory fresh if you ask me ...

no no charlie, i am not planning to sell my K! come on! i've been a hard user of a VW T3 '82, vespa 200 '88 and i know what does it mean to fix things and have those damn nails black for the most of my days (having people in the office looking at them with a weird face haha).

i just run out of money for now and winter is coming which means that i wont be albe to fix anything... but no no, i am not giving up!

as for now i know i have to start with the RH cover and rivet diagnosis.

it's on!

good man .....oi ..oi ..oi !