Splines let go tonight

[lhead]

I've had this '93 1100 rs for less than a month. No typical symptoms other than a small amount of noise when the clutch was out in neutral. I was going up a hill and accelerating and crunch/bang and no more forward motion. I've ridden this bike gingerly not knowing the history of spline lube or whether it had been done at all. It's got 80k on it. Just last week I bought a container of Guard Dog GD525 with the intent of doing the splines asap.

The good news? It happened less than a mile from home and the tow truck driver was great, put it on the flatbed, strapped it down and charged me $85 for the tow. I work 16 miles away and it could have happened in the parking lot at work.

I'll keep everyone posted on the progress tearing it apart including pics.

When these things happen, what typically lets go? Transmission input shaft? What are my options if the input shaft is shot?

Moral of the story? Lube them splines!

Charlie

[Scott_]

More often than not, it's the clutch disk(the female half of the equation) that gives up. Funny how that seems to be the case..... :hmm:
Give the trans shaft a good inspection when you have it out though.
Duck has a good write up in the Lieberry for the job.
 

[Rick G]

Being a K1100 I would suspect either the rear uni joint of the drive shaft or the clutch splines.  The way you describe the noise have a look first at the drive shaft.

[argent brick]

Oh crap. Well, they say keeping an old bike on the road is a labor of love.

How many miles should you be able to go before a tear down for a spline lube?

[leecow]

Mine is coming up on 85k and service records indicate that it's probably had the full spline lube work at least 3 times before I bought it. Put 25k on it last year and am just about done with the lube. All splines looked pristine.

[frankenduck]

Being a K1100 I would suspect either the rear uni joint of the drive shaft or the clutch splines.  The way you describe the noise have a look first at the drive shaft.

The front U-joint is identical and just as frail but I agree that it's more likely that it's a U-joint.

[lhead]

Thanks for the input everyone. So, are the u joints available and not prohibitively expensive?

[Howard64180]

I was lucky.  I got a final drive unit, drive shaft (with both UJs) and swinging arm off Ebay for around 80 GBP.  So that's wehre I'd be looking if I needed another.

[Howard64180]

Or even 'where'

[Scott_]

You really need to start disassembling to actually find out what broke, and removing the FD is the 1st step.
If it is part of the drive shaft, you will know it before you have to remove the transmission.
If it is just a u-joint, you may have to search for a vendor to buy it and a machine shop to change it. You cannot get them from BMW.
If the u-joint yoke broke, your limited to replacing the drive shaft assy, new or used, your choice.
If the drive shaft assy is intact, then the transmission has to come off to look at the clutch.

[frankenduck]

If you buy new from BMW you have to buy both halves of the drive shaft - part 26112325746 - only about $720! :yow

[lhead]

Thanks again guys. I'm tearing into it tomorrow morning. I'll let everybody know what I find with pictures.

BTW, I saw an interesting video on youtube going into the reasons for failures in the BMW drivelines.

Charlie

[frankenduck]

If he thinks the drive train is such a poor design he should sell his K75, buy a Jap bike and make videos about how wonderful Jap bikes are.

What's he doing riding a K75 at 35 MPH in fifth gear?   :hehehe

Clutch/transmission splines being out of alignment isn't caused by replacing the clutch. :nono

I've never heard of front drive shaft splines wearing out.  They don't slide against each other due to the circlip in the splines - which is why it's there. 

The rear drive shaft splines wear because they slide under load - like when the rear end moves up and down when accelerating or engine braking.  Kept properly lubricated, they will easily last 100,000+ miles.  Wear item or design flaw? You decide.

I guess that vid has some entertainment value though.

[Rick G]

The reason the front yoke clips in is so it lines up correctly with the center of the pivot point of the swingarm and stays there, it cant be let to slide as that will cause rapid failure of the uni joint and splines.
If you suspend the drive shaft in center of the swingarm (where the spline keeps it ) there is barely any longtitudal movement, maybe .1mm.
The splines often fail because when you have only one uni joint there is a rotational speed difference between the yoke and the shaft (as the uni loint moves through it various phases) which causes a hammering effect to the spline at both splines but is far more pronounced at the rear spline because the shaft is much heavier and so hammers much more violently.
If you look at a spline that is getting close to failure there is a lot of plastic deformation at the front edges of the spline on the front face of the shaft.
I have said here once that I have a theory about why the rear uni joint is often the one that fails on a paralever drive shaft and that is because the back yoke is not clipped in place as the front one does and that makes the center of the uni joint not concentric to the pivot center of the rear pivot and that makes for the hammering effect even though the shaft has 2 uni joints but it hammers in the joint and not at the spline. Result Disaster as has been seen here and elsewhere.
To give an example try to keep the uni joint at close to its maximum angle when holding it in your hands and then rotate the shaft while holding the joint at that angle you will feel it as very loose then tight and its very jerky as it turns. You get that jerking even at low angles and then multiply it for the RPM and it can become very violent as you should be able to imagine. If you have a uni joint at both ends then if the joints are phased correctly there is no jerkiness between the yokes at either end as one is cancelled by the other but the shaft will move at differing speeds at various places through each rotation and not be noticed.

Lecture over I hope I explained well and didnt mean any offence to anyone.

[frankenduck]

The very rear splines are clipped onto the FD input splines.  It's the intermediate drive shaft splines that don't have a clip.

After poking around a bunch and reading engineering stuff on the topic I'm of the opinion that one thing that impacts the U-joints is whether or not the front and rear U-joints are in sync.  When I pulled my RS apart to spline lube it (and I"m pretty sure it hadn't been pulled apart since the factory) the U-joints were not in sync so I suspect the engineers may have intended them to be in sync but that notion didn't make it  to the factory floor.

I always sync my U-joints on reassembly. It certainly can't hurt.

That and the fact that the U-joint bearings are more or less the same as the "not so great" pivot bearings.

There's my lecture. :yes

[Rick G]

I got the unis out of sync when I put the K1100 back together and I could really notice the difference when I put it right.
If the rear uni isnt clipped in properly the centers dont line up and considering that it is a lot easier to put the rear drive in with the central spline already together i reckon that is where it happens because if it is done that way the rear yoke cant be clipped in place as it needs to be.
I have found it very difficult to get the shaft phased correctly while putting the drive back on with both uni joints clipped into place. I need two people to do it. have you found an easy way.
It puzzles me that the splines were not made to only go in one way.

[frankenduck]

Agreed. It's kind of a PITA to get things back together even unsync'd,  I use a paint pen to mark things ahead of time and get things lined up.  Getting the splines and pivot bearings all lined up to get things back together is an act of contortion.

My K1 has a new drive shaft installed by a dealer before I bought it and that's even worse because the front portion is shorter so you can't even prop it up on that little bridge in the swing arm. Had to stuff a rag under it to hold it up and then once the splines had started to mate I pulled the rag out.

[lhead]

Duck called it.

It's not the splines after all. The front driveshaft u joint broke. A portion of the yoke remains on the trans output shaft up in the swingarm. In the pics, you can see the heat discoloration on the ends of the affected u joint.  The splines on the FD end of the shaft and the splines on the FD itself look ok to me.

It looks as though I'm going to need a new driveshaft. Even if I could source a u joint, there's the broken yoke.

Suggestions?

Thanks,

Charlie

[Scott_]

Even if I could source a u joint, there's the broken yoke.

And the other halve that is beat to $#$%%.

Time for a drive shaft.