2V K100 1986
The engine runs nicely at higher revs, but with the throttle closed it makes this rattle noise.
Before I start looking around in there I read up in Haynes and Clymer. I read that this kind of noise could be because of excessive cam shaft end float/cam shaft thrust bearing beyond wear limit. My concern is, when I open it I'm going to check cam shaft end float. The remedy according to the manuals is "replace the cam shaft"

Why? Is a thrust bearing not a wear part?

I'm hoping that I'll need only to replace the the chain guides, but I may as well check all other stuff for wear while I have the engine open.

Kafflut wrote:2V K100 1986
The engine runs nicely at higher revs, but with the throttle closed it makes this rattle noise.

Can you post an audio file or a YouTube link containing the noise?

Kafflut wrote:2V K100 1986
The engine runs nicely at higher revs, but with the throttle closed it makes this rattle noise.
Before I start looking around in there I read up in Haynes and Clymer. I read that this kind of noise could be because of excessive cam shaft end float/cam shaft thrust bearing beyond wear limit. My concern is, when I open it I'm going to check cam shaft end float. The remedy according to the manuals is "replace the cam shaft"

Why? Is a thrust bearing not a wear part?

I'm hoping that I'll need only to replace the the chain guides, but I may as well check all other stuff for wear while I have the engine open.

Hi 
So I too have had this rattle at idle and was quite worried until I think I have it sorted . Anyway my 1992 k100rs had a real noises rattle when I first got it going after I bought it siezed . Anyway to cut a long storey short I got the bike running and was concerned about a lot of rattle at idle and I was also having to keep the choke on most of the time too. 
So after getting it through the MOT I noticed the bike was over heating in town traffic and radiator fan was not coming on . I tested fan and it was working and found the temp transmitter behind radiator was not so fan would not come on . I wired the fan in direct through a dash mounted switch and disconnected the temp switch . 
I started the bike up and it sounded different , rattled for about a minute then it smoothed out and sounded quite normal . I drove it around for the day as it idled perfect with no choke and no rattle. 
I went back to manual to read up on the cooling system to see what I had done and if I could make sense of it . So what I gathered was on start up the Motronic sets the fuel and air mix according to the coolant temp !  So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

Peterk100rs wrote:
 So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

That's radical. How do you know when to activate the fan?

Laitch wrote:

Peterk100rs wrote:
 So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

That's radical. How do you know when to activate the fan?

A 92 RS has temp and fuel guages.

Al

92 is 16 valve with Motronic control system, your 86 is a 2 valve per cylinder with LE Jetronic control system.  This "fix" is unlikely to work for you.

Low speed/idle rattle can be the alternator monkey nuts, or the cush drive in the water pump/oil pump drive shaft (usually settles when the bike warms up). You can use a stethoscope or a long screwdriver to try and locate where its coming from, ear against the screwdriver handle, tip of the screwdriver pushed against the engine cases, move it around till you can hear it clearly.

Al

AL-58 wrote:

Laitch wrote:

Peterk100rs wrote:
 So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

That's radical. How do you know when to activate the fan?

A 92 RS has temp and fuel guages.

At what point on the gauge is he activating the fan, AL?

Laitch wrote:

AL-58 wrote:

Laitch wrote:
That's radical. How do you know when to activate the fan?

A 92 RS has temp and fuel guages.

At what point on the gauge is he activating the fan, AL?

No idea, that would be personal choice/opinion.  My K11 sidecar has a manual switch fitted as my temp gauge heads to the red very quickly in slow traffic or hot conditions.  i hit the switch as soon as it starts heading north and leave the fan on till the slow traffic etc has finished.

Al

Peterk100rs wrote:
....
I went back to manual to read up on the cooling system to see what I had done and if I could make sense of it . So what I gathered was on start up the Motronic sets the fuel and air mix according to the coolant temp !  So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

"Temp switch" aka Temperature Control Unit simply switches the fan on and off. It has nothing to do with the Motronic or fuel/ignition. The only correlation is that the both get their signal from the temp sensor located on the stub just behind the radiator.

Holister wrote:

Peterk100rs wrote:
....
I went back to manual to read up on the cooling system to see what I had done and if I could make sense of it . So what I gathered was on start up the Motronic sets the fuel and air mix according to the coolant temp !  So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

"Temp switch" aka Temperature Control Unit simply switches the fan on and off. It has nothing to do with the Motronic or fuel/ignition. The only correlation is that the both get their signal from the temp sensor located on the stub just behind the radiator.

Yes sorry wrong term ,temp sensor is what I meant to say . With this disconnected the bike starts  differently. Sounds smoother and only rattle for a short time. I think the Motronic does regulate fuel air mixture at cold start or at least thats what the manual says. What I forgot to mention is that I also have the connector to the sensor bridged as I was checking if the fan was working by connecting it directly to the battery and forgot to remove it afterwards. I put a manual fan switch on the dash which i switch on as i come into town. Maybe its because I have the sensor bridged , Im not sure but all I can tell you thats its nowhere near as noisy on cold start. In general it runs better . Maybe its just the bike is now cleared out better after a few good runs as it had lay up for six years. 
I don't have experience on theses bikes apart from spending most of last month bringing back from the dead. Lovely bike to ride and really enjoying it .

If the rattle stops when the throttle is just off idle (or when the fast idle lever is operated) then I'd do the easy thing and check the throttlebody balance before doing anything else.

Peterk100rs wrote:

Holister wrote:

Peterk100rs wrote:
....
I went back to manual to read up on the cooling system to see what I had done and if I could make sense of it . So what I gathered was on start up the Motronic sets the fuel and air mix according to the coolant temp !  So with me disconnecting the temp switch I have basically changed this . The bike starts up , rattles for a minute then runs fine all day . 
I know many will disagree with this but it works and I can't see why I would change it . I have driven the bike at motorway speeds and found it smooth and powerful . So that's my experience with the rattle.

"Temp switch" aka Temperature Control Unit simply switches the fan on and off. It has nothing to do with the Motronic or fuel/ignition. The only correlation is that the both get their signal from the temp sensor located on the stub just behind the radiator.

Yes sorry wrong term ,temp sensor is what I meant to say . With this disconnected the bike starts  differently. Sounds smoother and only rattle for a short time. I think the Motronic does regulate fuel air mixture at cold start or at least thats what the manual says. What I forgot to mention is that I also have the connector to the sensor bridged as I was checking if the fan was working by connecting it directly to the battery and forgot to remove it afterwards. I put a manual fan switch on the dash which i switch on as i come into town. Maybe its because I have the sensor bridged , Im not sure but all I can tell you thats its nowhere near as noisy on cold start. In general it runs better . Maybe its just the bike is now cleared out better after a few good runs as it had lay up for six years. 
I don't have experience on theses bikes apart from spending most of last month bringing back from the dead. Lovely bike to ride and really enjoying it .

I'm a little baffled. With the sensor disconnected the motor should not start. The Motronic will see this as infinite resistance and thinks its really cold so it pours on the fuel for a cold start, flooding the engine. When you say you've "bridged the connector to the sensor" what do you mean? Bridged the 2 connections in the plug or bridged the plug connections to earth.

Either way, I really don't think this arrangement is ideal. I would suggest reconnecting the the temp sensor for a few reasons. I doubt its got anything at all to do with the rattle you're hearing. The Motronic will not be able to set the correct injection pulse time and this is most important at cold start. There is a safety measure built into the Motronic which prevents the engine starting when its overheated and it won't get that signal from the sensor when it's disconnected.

If you suspect something is wrong with the temp sensor, then test it and if faulty, replace it.

AL-58 wrote:No idea, that would be personal choice/opinion. 

That's why I asked him first, AL. I thought you might be riding pillion when you answered.

Okidoki - My question has generated a lot of response.

I can say without fear of contradiction my problem is not related to temperature - it rattles when cold and it rattles when warm. Maybe a smidgen less when warm, but in my opinion that may be due to higher revs and there's more consistent tension on the timing chain - less lurching in that mechanism.

I'll record the sound and try and post it.

The other question was: Is the cam shaft thrust bearing not a wear part? Why must I replace the cam shaft(according to the manual) if there is excessive end play?

From what you describe, it sounds like the timing chain and/or guides. I've done two and both times rattle noise from the front was a lot less after. Its quite apparent that it comes from the front timing chain cover. Take a look at my thread on this.
Here's a recording of the noise coming out of mine.

One thing to remember when thinking timing chain rattle is The crankshaft ALWAYS drives the camshaft, cams don't slap about throwing tension on and off the chain except on extremely high lift and long duration cams on single cylinder engines and even then it is highly unlikely.  There may be other reasons for the chain to be noisy like a slack back run when tensioners are badly worn.

The camshaft must be replaced because to replace the cam bearings the complete head would need to be replaced, there are no slipper bearings just the very cheap bearings machined direct to the head casting.

The most likely rattle will be from the tension spring on the main output shaft gears. Removal of the cam cover and then the chain cover may reveal some issue with the chain or tensioners and rails.

Holister wrote:Here's a recording of the noise coming out of mine.

I guess my tolerance for noise is high; that sounds good to me. I suppose there's a possibility this auditory gift of mine will require frenetic action somewhere down the line far, far from home. Maybe the food will good there and I'll be out of the rain. I'll bring a poncho, a tarp, a spirit stove and some tea along for good measure though.

Thanks Rick, Laitch & Holister

I guess that makes my mind up for me - I'll forget about the cam shaft end float for now because it seems most likely timing chain or related components.

Thanks for the sound-byte  and thanks for the link, Holister

I'll post what I find. It won't be soon I'm going on a long ride later this month - I don't expect it to give problems

RicK G wrote:One thing to remember when thinking timing chain rattle is The crankshaft ALWAYS drives the camshaft, cams don't slap about throwing tension on and off the chain except on extremely high lift and long duration cams on single cylinder engines and even then it is highly unlikely.  There may be other reasons for the chain to be noisy like a slack back run when tensioners are badly worn.

Thanks Rick

I understand the "crankshaft always drives the camshaft"

Does that mean that there is never a possibility of the chain getting ahead of the drive sprocket for a millisecond, for example?

My thinking was: assuming there is slack in the chain between the drive(crank) sprocket and the driven(cam) sprocket not taken up by the tensioning mechanism, it could cause a minuscule jerk when the slack is taken  up. If this were the case it is more likely at low revs. My further thinking was: not that this "jerk" causes chain noise but that maybe a valve(s) is not always in an optimal position when the spark occurs and that irregular firing may cause engine noise like pre-ignition does. Then again the variation in valve position will probably be too small to have an effect.

My thinking now: My earlier thinking was nonsense, straw-clutching at best 

Does that mean that there is never a possibility of the chain getting ahead of the drive sprocket for a millisecond, for example?

Correct. I doubt that would be possible even with a worn chain.
The timing chain doesn't seem to wear and stretch much. The two I've replaced were ok in fact the one out of the K1100 was like new. Where problems arise is with wear of the guides. This was significant on the 1100. If guide wear gets too bad, I guess the tensioner has trouble keeping the correct tension to the chain leading to a little bit of slack. But even so I think where the noise comes from is the chain not leading and trailing correctly on and off the guides and sprockets due to guide wear.

It just wont happen with a four cylinder. One of the inlet valves is always coming onto the ramp with a K. Like I was saying the single with a really lumpy cam will push the cam ahead of the crank at low speed and idle. Usually any engine with a cam like that wouldn't be usable at those low revs.

So I'm just putting in my penies worth here . I said earlier That i had disconnected the the,p sensor and bridged the connector. The first thing is the engine is more difficult to start i.e. : it back fires using the fast idle lever but starts when using the throttle. Normally before I made the change I just used fast idle and hit start .
So the only thing I can deduce from this experiment is that the temp sensor plays apart in the fuel air mix at cold start up. Secondly after re connecting the temp sensor I realised that the engine still sounds rattled at idle. But runs very smooth from 1500 rpm. So I'm guess this is caused by mechanical wear in bearings or guides within the engine . To me it sounds loudest at the crank ( right )side of the engine .
So I'm going to drain oil out and remove the cover to see if there is any play .
Then Im gonna remove rocker cover and do the same .
Im also gonna look into replacing the cam chain guides while I'm at it. 

Oh and I bought another bike during the week , its a 1989 K75s in mint condition. Been driving it all week and it s smooth and rides really well. Big difference in the two bikes.

You won't find anything behind the crank cover or the valve cover that will make a rattle. The valve clearances may need adjusting but you won't hear much noise from them. You won't need to drain the oil either but be careful taking the covers off as oil pools inside. There's a small spring on the inside of the valve cover. Careful you don't lose it.

There's plenty of info on the forum on replacing the timing gear. Do the chain as well. It's cheap enough and it's peace of mind. Also it's worth replacing the front crankshaft seal on the timing cover.

Consider posting a video with sound so we can get a better idea of what you're up against.

Cheers

Holister wrote:You won't find anything behind the crank cover or the valve cover that will make a rattle. The valve clearances may need adjusting but you won't hear much noise from them. You won't need to drain the oil either but be careful taking the covers off as oil pools inside. There's a small spring on the inside of the valve cover. Careful you don't lose it.

There's plenty of info on the forum on replacing the timing gear. Do the chain as well. It's cheap enough and it's peace of mind. Also it's worth replacing the front crankshaft seal on the timing cover.

Consider posting a video with sound so we can get a better idea of what you're up against.

Cheers

Thats interesting as I thought if this was loose that it would effect the running in general . But definitely worth checking . Ill do a video tomorrow and post it .

Holister wrote:There's a small spring on the inside of the valve cover. Careful you don't lose it.

To reinforce what Holister says; that spring earths the cambox cover to the rest of the engine. If you miss it out, BMW say you stand a chance of building up a static charge on the cambox cover and blowing the FICU when it discharges across the engine.

Dai wrote: BMW say you stand a chance of building up a static charge on the cambox cover and blowing the FICU when it discharges across the engine.

Or blowing your lunch if you touch it when you're grounded.

Remove the alternator and check the rubber cush drive. These rubbers are commonly called Monkey nutz. The noise they make can be very deceiving and this is sounding like that is your rattle.

Peterk100rs wrote:

Holister wrote:You won't find anything behind the crank cover or the valve cover that will make a rattle. The valve clearances may need adjusting but you won't hear much noise from them. You won't need to drain the oil either but be careful taking the covers off as oil pools inside. There's a small spring on the inside of the valve cover. Careful you don't lose it.

There's plenty of info on the forum on replacing the timing gear. Do the chain as well. It's cheap enough and it's peace of mind. Also it's worth replacing the front crankshaft seal on the timing cover.

Consider posting a video with sound so we can get a better idea of what you're up against.

Cheers

Thats interesting as I thought if this was loose that it would effect the running in general . But definitely worth checking . Ill do a video tomorrow and post it .

Not sure what you're referring to there. If you're talking about the valve clearances. No, they won't make excessive noise. Its a camshaft/shim system not an adjustable rocker. In the 2valve models they tend to get tight so are better set on the loose end of the tolerance range, particularly the exhaust valves. But I just noticed you have a 4v model so I doubt very much valve clearances will be an issue as they are practically set and forget.
If you're talking about the timing chain gear (under the front cover). Excessive wear will make a noise but it won't affect the performance. Timing chain is very reliable so there's never enough wear that would affect the valve timing. Any noise in this area will be usually due to chain guide wear and possible issues with the tensioner keeping the tension up as it gets to the end of play. Timing gear noise emanates from the front cover as you see in the video above. If your noise is coming from the right hand side its probably the alternator as rick mentioned.

Alternator Cush drive sounds about right . I'll get at that tomorrow . Thanks for all the help everyone . And also excuse my ignorance on working on K bikes as its a bit of a learning curve at the moment but I'm getting there .

RicK G wrote:Remove the alternator and check the rubber cush drive. These rubbers are commonly called Monkey nutz. The noise they make can be very deceiving and this is sounding like that is your rattle.

Thanks Rick , it sure does make sense of where the noise appears to be coming from . I'll have a look at the manual and have a go tomorrow .

Peterk100rs wrote:.... And also excuse my ignorance on working on K bikes as its a bit of a learning curve at the moment but I'm getting there .

I wouldn't lose any sleep over that. Many of us have been there. This is what the forum is for.

So i removed the alternator and found only two monkey nuts intact the rest where just basically dust.
So this looks positive i guess for being cause of rattle . So I've ordered two more sets and see how that goes , heres hoping

RicK G wrote:
The most likely rattle will be from the tension spring on the main output shaft gears. Removal of the cam cover and then the chain cover may reveal some issue with the chain or tensioners and rails.

Hello Rick

I met with rawdonball who's on holiday in Cape Town. We spoke about a lot of stuff and eventually also discussed my "rattle" He listened to the motor and concluded that for a high mileage k100 it's not-too-noisy Well there you go. Too cut a long story short I now believe the noise is either most likely in my head or it could be that tension spring you mention - torsional backlash? Thank you for steering me in that direction. In reading about it I found this drawing that helped me understand the concept better

Tapered helical and spur gears provide another approach. These gears have teeth cut at a slight angle to provide a tapered tooth form. An assembler adjusts the tooth clearance by moving the gears relative to each other in an axial direction.
One of the more sophisticated ways to control backlash is called gear train preloading. A torsion spring or weight on the last driven gear in a system loads one side of the meshing teeth to eliminate tooth clearance. The spring or weight travel, however, limits the amount of rotation of the last gear. For unlimited rotation, an auxiliary motor can provide the load rather than a spring or weight.
This method is especially useful for gear trains with many stages, where backlash is cumulative. Spring-loaded versions work best in low-torque, uni-directional drives.

Kafflut wrote:I met with rawdonball who's on holiday in Cape Town. We spoke about a lot of stuff and eventually also discussed my "rattle" He listened to the motor and concluded that for a high mileage k100 it's not-too-noisy Well there you go.

That's good news

Kafflut wrote:Thanks Rick, Laitch & Holister

I guess that makes my mind up for me - I'll forget about the cam shaft end float for now because it seems most likely timing chain or related components.

Thanks for the sound-byte  and thanks for the link, Holister

I'll post what I find. It won't be soon I'm going on a long ride later this month - I don't expect it to give problems

That is what I thought as well. I changed all my timing chain and related rails, and other bits and the noise persists. In my case it is the monkey nuts on the alternator which is on the list.

Well guesswhat, I managed to get my rattle on Youtube. The sound is not good - I think there's a lot of noise bouncing of hard surfaces of my garage

Listen for a tucka-tucka-tucka---- a less sharp sound when I release the clutch. It goes away when I pull the clutch in - this is especially noticeable in the first 5-7 seconds. I made the recording shortly after starting and adjusted the fast idle so the engine runs at just over 1000 rpm

I will appreciate your comments and suggestions

Can't play it.  Says the video is private.

Point-Seven-five wrote:Can't play it.  Says the video is private.

 Okay

I made sure I defined it as "public" in Youtube
I think the problem was that I did not do a "post" in Youtube - I have now
I edited the original post, deleted the video clip and added the latest.
Please let me know if you can play it now

It plays for me. I'd remove the alternator an take a look at the damper rubbers in there (monkey Knuts).

Yep that's very typical of a K Klutch. Don't be too concerned I have heard many a lot worse than that.
It is often caused when the diaphragm and wire ring need some lube on them and that when the clutch is engaged both are essentially floating.

Thanks for feedback RickG & Holister
Since the alternator is relatively easy to pull I will inspect the monkey nuts. I will probably replace the wear parts in the timing chain area.

I read in Clymer about "BMW Service Information Bulletin 11037 88 (2289)" which has to do with noise caused by the C-spring(17) and rubber(13) see
below I googled for that service bulletin but without success. Any idea how one can get to see it?

You can't - the output shaft is all riveted up. I'm with Rick here; it's highly unlikely that the output shaft rubber is faulty.

Kafflut wrote:. . . which has to do with noise caused by the C-spring(17) and rubber(13) see
below I googled for that service bulletin but without success. Any idea how one can get to see it?

Click on this link then scroll down to section heading Time for the engine inspection. At the end of that section, you will see a photo of that part and read a little about it.

Laitch wrote:

Kafflut wrote:. . . which has to do with noise caused by the C-spring(17) and rubber(13) see
below I googled for that service bulletin but without success. Any idea how one can get to see it?

Click on this link then scroll down to section heading Time for the engine inspection. At the end of that section, you will see a photo of that part and read a little about it.

Thanks for the link, Laitch
The output shaft work is something I may tackle one day, when I've tried everything else. I suspect that the C-spring on mine is most probably like the one in this photo



For now I'll be guided by the comments I've received - alternator & then the timing chain mechanism. Immediately following the output shaft section of the link there's a section on timing chain. I found that bit very useful too.

I had an '85 K100RS with a grumble at idle especially when cold.  I did diagnose it as the output shaft, and came across the improved 1988 (??) version of the output shaft on ebay, and won it for $5.  Put that in one afternoon (it's a little more complex than changing spark plugs) and that solved my problem permanently.  Just something to consider for future entertainment....

club_c wrote:I had an '85 K100RS with a grumble at idle especially when cold.  I did diagnose it as the output shaft, and came across the improved 1988 (??) version of the output shaft on ebay, and won it for $5.  Put that in one afternoon (it's a little more complex than changing spark plugs) and that solved my problem permanently.  Just something to consider for future entertainment....

Was it a 12 rivet shaft that you won for $5 ?????? Did the original 6 rivet shaft show any evidence of loose rivets or do you think your noisy idle problem was solved by fitting an output shaft which had less wear in the anti backlash arrangement?

Yes it was a 12 rivet one I got so cheap. Once removed, my original 6 rivet had loose rivets that I could not tighten up.  The loose rivets was definitely the problem.

club_c wrote:Yes it was a 12 rivet one I got so cheap. Once removed, my original 6 rivet had loose rivets that I could not tighten up.  The loose rivets was definitely the problem.

Cheers Mate - what a wonderful break. Good on you. Enjoy it

Did you by any chance check the state of the anti backlash components on the shaft you removed?
I would love to hear from anyone who can comment on any distinguishing features / symptoms between the loose rivet problem and the anti backlash wear problem? Difficult as I suspect they often occur together and both would be contributing to noise to varying extent depending on the severity and circumstances. E.g hot idle, cold idle and likewise acceleration at low revs....

Oh boy. I'll bet that was 3 years ago. I do recall some oblong wear on the clip on the 6 rivet shaft and a clean clip on the 12 rivet. Does that help.

Is there a guide or a how to here on this site or anywhere for this? Preferably a video? This is next for me after I finish the new fan and installing the trunk.