What's this, where should it connect?

[Ingo]

Taking brick apart, found this loose under tank. Other end goes to breather in top of valve chain cover and (presumably) to vacuum. Can not find any loose hose or tubing in area of this end...

This is my first post, please excuse any mis-steps of mine.

Had this 1992 K1100LT since about 2006, K100RT before that, coming from R90/6 (souped up to R90/S specs due to it came on a S-frame). Current moto has 44K miles, vibrates like crazy, will address once this is back together, had engine output seal bye-bye...

[Scott_]

You can remove it and cap the line where it connects at the top of the block.
I see in your picture that a P.O. has installed "the cup" so what you have is no longer needed.
Originally it connected to the gas tank vapor vent line, so that fuel vapors were drawn into/thru the block and then drawn into the intake air stream for combustion.
Problems occurred when people overfilled the fuel tan and liquid gas would then make it's way down into the oil and cause problems, so BMW did away with it.

[Ingo]

Very good, thank you. Will remove since there's waayy too much stuff under the tank, it's very crowded.

[Laitch]

Current moto has 44K miles, vibrates like crazy, will address once this is back together . . .

If the moto vibrates in general instead of at a specific place like the front end, consider inspecting the driveshaft u-joints for looseness, stiffness or being out-of-phase, if you haven't done that yet.

[The Mighty Gryphon]

Check the steering head bearings, front wheel balance and the engine mounts.  How old are the tires?

Run the engine for a couple minutes to get the headers hot and then squirt a little water on them.  Does it boil off of all four with equal enthusiasm?

[frankenduck]

Getting rid of vibration: Sync the throttle bodies and make sure the little black rubber caps on them are not cracked and leaking air.

If the throttle bodies won't sync then a leaking boot between the TBs and cylinder head may need replacing.

[Ingo]

Thank you guys for the responses.
Laitch: I don't know what "out of phase" means...
It is definitely the engine causing vibration, pull clutch and there's nothing while rolling. Synchronizing is due once I have her back together. It's going to be a while. Pulled engine apart, was shocked about gaskets and seals and head gasket prices, spent $ 1500.- so far. Wear is marginal, rod bearings are hardly run-in. P.O. must have done oil changes regularly. I only used synth oil, seems to be doing good. Rubber boots on intake look fine, so do the plastic connections. On re-assembly I will check valve play, make sure mechanically everything is good there there. Right now cleaning pistons and going to check their weight (balance). Have to wait for ordered parts to come in. Then I will be working again with little time for wrenching. Took 2 weeks off to work on bike, not nearly enough time...

[The Mighty Gryphon]

Drive shaft phasing refers to the alignment of the two u-joints.  The u-joints need to flex the same way in unison.  This will allow the drive shaft to rotate around a stable axis.  Not only does phasing prevent drive shaft vibration, but out of phase u-joints will have a tendency to self destruct. 

[frankenduck]

Drive shaft phasing refers to the alignment of the two u-joints.  The u-joints need to flex the same way in unison.  This will allow the drive shaft to rotate around a stable axis.  Not only does phasing prevent drive shaft vibration, but out of phase u-joints will have a tendency to self destruct. 

"The inner can slip."    

No, the insulating rubber flexes.

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/dsphase/dsphase.htm

[The Mighty Gryphon]

It's worth noting that there is a spring ring in the splines at the transmission end of the drive shaft that maintains the location of the drive shaft on the output shaft of the transmission. 

You need to push the drive shaft onto the output shaft until the ring snaps into the groove on the output shaft.  If you don't, the the front half of drive shaft can float down toward the final drive and the u-joint can hit the inside of the swing arm when the swing arm is at the extremes of rear wheel travel. 

[Ingo]

What a beach! I didn't plan on taking that apart, too. But as I'm into it this far I might as well make it complete. I can see why the "phasing" would be important. Though it "should" be right, I very much doubt it's ever been apart since it left the factory.
So I've got to take the swing arm off the gear box, right? There is no getting to it from the rear end only?

[frankenduck]

What a beach! I didn't plan on taking that apart, too. But as I'm into it this far I might as well make it complete. I can see why the "phasing" would be important. Though it "should" be right, I very much doubt it's ever been apart since it left the factory.
So I've got to take the swing arm off the gear box, right? There is no getting to it from the rear end only?

Yes, you need to pull the swing arm to see the front U-joint.

It's a heck of a lot easier and much less work than replacing the head gasket.

Before reassembling it helps getting it right if you put some paint or whatever on the rear face of the front half's splines.

[Laitch]

Pulled engine apart . . . What a beach!

Though it "should" be right, I very much doubt it's ever been apart since it left the factory.

You've completely dismantled the engine but unbolting the driveline is a beach?   You've got to be meaning it's una playa hermosa.

The u-joint phasing might be out when it was reassembled after being given a transmission input spline lube or the u-joints themselves might be worn out from he-person throttle and clutch abuse, or there just might have been some loose driveline bolts somewhere. 40K is early for an output shaft seal problem, so maybe all these components were made and assembled on Fridays or Mondays. 

[frankenduck]

It's worth noting that there is a spring ring in the splines at the transmission end of the drive shaft that maintains the location of the drive shaft on the output shaft of the transmission. 

On 4V bikes both the front and rear halves of the drive shaft have circlips in the splines.  Any back and forth occurs in the intermediate splines.

https://www.realoem.com/bmw/enUS/showparts?id=0536-USA-09-1992-89V2-BMW-K_1100_LT_0526,_0536_&diagId=33_1658

[frankenduck]

40K is early for an output shaft seal problem.

It's 30 year old rubber. Seals can get old and leak regardless of the odometer.

[Laitch]

Seals can get old and leak. . .

I saw an old seal at the zoo once, long ago but I was very young at the time and it might have actually been middle-aged.

[Ingo]

Well, a beach nevertheless. Dismantling an engine is nothing new to me, I think I've taken almost all my vehicles engines apart over the years. I keep them for long term. 2 yap bikes and 3 cars where exempt. Last was my souped up WRX, just under 400 hossies proven on dyno afterwards ( and that was 20KMiles ago). It's just that this drive train is new to me and I'm not sure (yet) what I'm dealing with. Do I need parts (seals, circlips...) for this?

[frankenduck]

Well, a beach nevertheless. Dismantling an engine is nothing new to me, I think I've taken almost all my vehicles engines apart over the years. I keep them for long term. 2 yap bikes and 3 cars where exempt. Last was my souped up WRX, just under 400 hossies proven on dyno afterwards ( and that was 20KMiles ago). It's just that this drive train is new to me and I'm not sure (yet) what I'm dealing with. Do I need parts (seals, circlips...) for this?

Some moly-based spline lube grease. No need to replace any seals or circlips.

It doesn't always happen but the final drive pivot bearings have needle bearings held in place by plastic bearing races (cages) that like to disintegrate so they might look like this when you take the final drive off.


You can get better bearings here:
https://www.beemershop.com/product/ei-paralever-bushing-kit-for-r80r-r100gs-r100r-k100rs-k1-k1100rslt.html

[Laitch]

Both fore and aft boots could be cracked, and the rubber of both lower arm bushings might be rotted requiring replacement of those bushings, too. What is said about old seals also applies to old rubbers. Beware!  

[Ingo]

You know what's worse than a hole in the rubber?

[Laitch]

Yes.

[frankenduck]

You know what's worse than a hole in the rubber?

Drive shaft out of phase.

[The Mighty Gryphon]

The front circlip on the drive shaft is important. 

The guy I sold my first K100 16 valve to did the splines but didn't get the front end of the shaft locked in place on the transmission output shaft.  It slid toward the final drive and made a loud clicking sound when he ran the engine in gear on the center stand.

Those circlips are important because they prevent the sliding contact at the transmission and final drive ends of the drive shaft that cause all the wear on the final drive spline in Monolevers.  With all the sliding being localized at the splines that connect the two halves of the shaft, the extended contact area of that spline spreads the load and reduces the pressure on the spline faces which reduces the wear.

[frankenduck]

The front circlip on the drive shaft is important. 

The guy I sold my first K100 16 valve to did the splines but didn't get the front end of the shaft locked in place on the transmission output shaft.  It slid toward the final drive and made a loud clicking sound when he ran the engine in gear on the center stand.

Those circlips are important because they prevent the sliding contact at the transmission and final drive ends of the drive shaft that cause all the wear on the final drive spline in Monolevers.  With all the sliding being localized at the splines that connect the two halves of the shaft, the extended contact area of that spline spreads the load and reduces the pressure on the spline faces which reduces the wear.

Both the font and rear circlips being engaged are important on the 4Vs. And aside from allowing spline sliding at the ends it also screws up the drive shaft geometry if the ends are loose because the ends aren't as far onto the splines as they should be when the circlips are engaged.

[daveson]

+1 Gryph

But I wanna throw something into the mix that I read about monolever bricks way back just before I got one. Because the drive shaft universal joint and the swing arm pivot points are concentric, there's no sliding going on, which is one of the advantages of the compact drive system, and probably still very unusual. Hopefully I've said that right.