Noisy Cold Starts - 1987 K100RT

[Reecehk]

Hi, I have had my 87 K100RT for about 4 years now & have probably spent over $3000 in parts & accessories plus a lot of time:

The bike has always had a clunking sound when it's cold but over the years & 50,000k's later it is getting a little too loud, once the bike is warmed up the noise is gone & runs quiet & smooth.

Trying to describe a noise is not easy so I recorded it in mp3 format that can be downloaded here:

http://www6.rapidupload.com/d.php?f...&filepath=38051

If anyone can offer some advise here I would really appreciate it, I live in the country (South Australia) so trying to get to a BMW dealer is not easy, let alone the cost just to have them check it out!

Many thanks for any help/advise in advance,

Reece.

[bmw_rider]

I can see the file upload site, but can't locate a way to download or play the file.

[Reecehk]

Hi, on the rapidupload page, top left is "Download file", click on this & it should start downloading, if the same screen appears click again, I just tried & it worked the second try, otherwise here:

http://hyperupload.com/download/020b61b717/K100_Cold_Start.rar.html

Many Thanks.

[Dennis Andress]

I couldn't listen to your audio clip so I'm just guessing here...

 

The real early K bikes had a problem where the output shaft was shimmed too lose and would make a noise like that. My 85 had the problem and the noise got worse when the engine was cold. If the noise changes when you pull the clutch in you might want to have somebody look at it.

[Reecehk]

Hi, the noise seems to be between the engine & gearbox, It is very loud sort of behind left of the gear lever, so you are probably correct, I have just replaced the final drive spline, tail shaft, output shaft, (spline stuffed again) and clutch plate, the input shaft spline was ok if I remember. Could you please elaborate on the shim problem, for reference I have the Clymer manual.

Funny that when the bike has warmed up & running the noise goes away, who ever had the bike before failed to use the BMW white grease on the splines, sure cost a penny to fix them!

Thanks.

[pfetter]

I have the same year and model bike, actually same color as in your picture. I also have a noisy cold running sound and then it goes away. I have only put about 100 miles on thebike since I purchased it (shame on me), I also have noticed that the bike seems to have a whine coming from it somewhere, I did not know if it was a normal BMW sound as this is the first BMW I have owned. When you did the splines on your bike did you do the front ones also or just the rear. AT this moment I am dealing with a spinning sprage clutch that will not turn the engine over. I have seen on the forum what to do about it and am going to follow the recommendations as soon as I can get someone to help me bump start it.

[Reecehk]

Hi Pfetter, as far as the gearbox is concerned I replaced the gearbox output shaft as the spline was stripped, the previous owner just did a quick fix by installing a new clutch plate only, the gearbox input/engine output seemed ok at the time.

My engine does make a kind of whistle/whine but I think that is normal, has been there since I got the bike, trying to locate a noise isn't easy & trying to describe it even worse!! It could be the timing chain, try listening at the cover, about all I can think of besides a shot bearing and that could be anywhere!

What you could do to start engine is place bike on center stand, put in 5th gear, ignition on, and rotate back wheel by the tyre, if it starts quickly pull clutch in, however it could be dangerous, the sort of thing I would try but not recommend!

I haven't tried starting and pulling clutch in to see if the cold start noise disappears yet, will have to give it a try.

Cheers.

[Reecehk]

Just tried pulling the clutch in while running cold, it definitely changes the tone of the noise & decreases volume slightly, but it's still there! Don't know if that's good or bad!

[Dennis Andress]

Hi, the noise seems to be between the engine & gearbox, It is very loud sort of behind left of the gear lever, so you are probably correct, I have just replaced the final drive spline, tail shaft, output shaft, (spline stuffed again) and clutch plate, the input shaft spline was ok if I remember. Could you please elaborate on the shim problem, for reference I have the Clymer manual.

Funny that when the bike has warmed up & running the noise goes away, who ever had the bike before failed to use the BMW white grease on the splines, sure cost a penny to fix them!

Thanks.

 

It looks like I should have said counter shaft instead of output shaft. It's the shaft at the rear of the engine that the clutch housing bolts to. I don't remember much about why it needed to be shimmed.

 

From what you are describing I don't think the noise you have is the same as I'm talking about. But, from the description of the work you've done recently, I wonder if the gearbox or clutch assembly is out of align after reassembly.

[Reecehk]

Hi Dennis, I would think that if I got the clutch etc out of alignment it would have excessive vibrations, the noise was there prior to the work done, just more time has past & gotten louder, unusual I would have thought that after warm up the noise goes away!! I'm just not looking forward to taking the bike off the road again & strip down! Maybe if I have to I will remove the rear wheel, final drive, tail shaft, swing arm, gearbox & clutch assy. then start the bike and see if the noise is there, this would atleast nail it down some!

Thanks.

[Dennis Andress]

Hi Dennis, I would think that if I got the clutch etc out of alignment it would have excessive vibrations, the noise was there prior to the work done, just more time has past & gotten louder, unusual I would have thought that after warm up the noise goes away!! I'm just not looking forward to taking the bike off the road again & strip down! Maybe if I have to I will remove the rear wheel, final drive, tail shaft, swing arm, gearbox & clutch assy. then start the bike and see if the noise is there, this would atleast nail it down some!

Thanks.

 

Keep in mind that any pressure placed on the clutch assembly from the tranny or engaging the clutch will affect how much the counter shaft is free to move along it's axis. You might be able to check axial run out by measuring with a dial micrometer against the clutch assembly while prying (gently, of course) the assembly fore and aft.

 

The problem could also be coming from the transmission. Maybe the noise would change if you tried a high quality gear oil. BMW's synthetic gear oil is pretty darn good.

 

Good luck

 

Dennis

[Reecehk]

Thanks Dennis, I will have to ponder the next move, what ever it will be a big job!

I will use the bike for a while since the noise goes away once warmed up for the day. I use SEA 80W 90 with 20% morey's oil stabilizer for gearbox & final drive, I'll recheck the gearbox level but I'm sure it's ok, I'm a little paranoid about things like that!

Just looked in the Clymer manual page 130-131 & seems like I could remove gearbox & clutch assy then leaving the motor in the frame just take off the Oil Pan then remove the lower crankcase half in order to remove the motor output shaft (if this is the problem)! Can this be done? what do you think!

Cheers.

[James Clark]

Doesn't BMW spec negative end play for K100 input shafts when cold? Could this be the source of the noise?

[Dennis Andress]

Just looked in the Clymer manual page 130-131 & seems like I could remove gearbox & clutch assy then leaving the motor in the frame just take off the Oil Pan then remove the lower crankcase half in order to remove the motor output shaft (if this is the problem)! Can this be done? what do you think!

Cheers.

 

That's pretty much the way the dealership did it years ago on my 85. You'll have to take the oil/water pump assembly off too. Be aware that the counter shaft will come out with the bottom of the lower crankcase half.

 

It really makes a lot of sense to check end play of the transmission input and output shafts along with that of the engine counter shaft as you take things apart on your way to taking the bottom of the engine off.

[Reecehk]

Thanks all, when I attack this job I think I will do as follows:

Remove all final drive gearbox clutch etc then start the bike & check for noise, if it's gone then it must be in clutch gearbox area or motor output shaft end play, if the noise is there then probably output shaft assy would be the problem.

It really boils down to "nothing ventured nothing gained", I will be checking every step of the way for endplay with gearbox input & output shafts!

I dare say when I start this job I will keep in touch.

Cheers.

[Dennis Andress]

Thanks all, when I attack this job I think I will do as follows:

Remove all final drive gearbox clutch etc then start the bike & check for noise, if it's gone then it must be in clutch gearbox area or motor output shaft end play, if the noise is there then probably output shaft assy would be the problem.

It really boils down to "nothing ventured nothing gained", I will be checking every step of the way for endplay with gearbox input & output shafts!

I dare say when I start this job I will keep in touch.

Cheers.

 

I'm not sure if running the engine without the transmission removed would be a good test. If the transmission is placing some kind of pressure against the clutch then your symptoms would change yet the cause may still be a lose counter shaft.

 

Dennis

[Reecehk]

I'm not sure if running the engine without the transmission removed would be a good test

When I referred to "Remove all final drive gearbox clutch etc" I should have said "Remove, final drive, transmission, clutch etc", So that only the engine was left in the frame, then start the bike & check for noise. I assume this would be the way to go? I would really like to know your opinion/procedure to nailing this down.

Many thanks.

[James Clark]

I'm not sure if running the engine without the transmission removed would be a good test

When I referred to "Remove all final drive gearbox clutch etc" I should have said "Remove, final drive, transmission, clutch etc", So that only the engine was left in the frame, then start the bike & check for noise. I assume this would be the way to go? I would really like to know your opinion/procedure to nailing this down.

Many thanks.

 

 

Be sure to hand off your beer and say "Watch this." before you try and start the engine.

 

 

How do you plan to anchor the starter motor?

[Reecehk]

Oh crap, don't tell me that this is mounted to the clutch housing/transmission assy, I guess I'll have to have a closer look in the manual ...... But I shall overcome!!

Edit: I love your avatar James!