The thread title says it all.    Over the time I have had this K1100 the exhaust has cracked 3 times with 3 different exhaust systems. I have one left and if it cracks I will probably burn the damn thing.
I have been told that it is the mount at the gearbox and the tightening sequence of the 8 nuts at the head.
The first system was welded about 3 times and the next twice then a staintune from a K100 was put on and discarded because it was far too rowdy for me and then the third one cracked about 4 months ago. I have one good one left and don't want that also cracking.
All info will be gratefully accepted including voodoo and witchcraft but I draw the line at using chicken entrails to find the answer.

rick to me, the 4th pipe takes a short cut ...
where as the first 3 bend then come back to some form of straightness before going to the welded merge
the 4th pipe is what I think ...short and takes a short cut at a weird diagonal towards the merge
I guess with heat expansion the angles and lengths don't all match up ..
I would much rather see it bend a little more at the bottom of the first bend  come up more vertically and then bend in line with the other three to hit the merge in parallel  with them ..
just my thoughts

My K100RS 4V had three exhaust systems replaced under warranty back in the 90's.  Around 1995 the original owner installed a Remus system and had the Motronic changed to non-cat.

I bought the bike in 2014, rode it one year and disliked the loud exhaust note of the Remus system.  I sold the Remus and installed a stock K100 exhaust.  Was a pretty easy retrofit. Does take a little bit of fiddling to get the stands to retract fully, but it's not a big deal.  Bike runs great and is much quieter.

One thing, because of the footpeg plate shape, the end of the muffler of the K100 exhaust sticks out about 3-4cm further than the correct muffler, but not enough to affect cornering.

It might be better for you to go back to the K100 staintune unit and go visit the Zorst specialist we all know and see about a baffle to drop it down to a nicer level of volume.
Otherwise take a broken one to a specialist to lengthen the shortest pipe and relieve the system, as Charlie is suggesting is the problem.

Bit hard putting the staintune back on as I don't think Smithy would let me take it back.
Just been playing with it now and I will probably put a sleeve of mild steel on it. It cant be seen but what gives me the shits is that BMW knew of the problem since the K100 16V and did nothing to fix it.
My opinion as to why it cracks is that the radius of the bend in the #4 is too tight and as it heats and cools it wants to open the bend out and that puts a big strain on it then it eventually cracks at the weld.
Might have a play with this one as there is nothing to lose.

the fortunate thing about all the 8 valve models is that the pipes are sleaved into the muffler allowing some movement

the welds just ask for issues

pitty you couldn't take one down to bert2 for some sleaving goodness ?

looking at the pipes no3 has a tighter bend than 4 ...I just think they took a damn big shortcut



pity the retainers are fixed to the pipes them selves ...this would defiantly let the system give a little as well

I also have a set of K100 header pipes and a collector and Laser muffler but it barks worse than the staintune.
Might bolt it all up to the spare head and see if I can come up with a solution.

When I had the exhaust off the K100 I had ordered new washers, studs nuts etc. The washers seemed very nice and soft and thick not sure of that makes any difference or not.

I have tried twice and put new copper rings in, I would expect it to make a difference. What I think contributes to it is riding on wet days where the exhausts get hot then quench as the bike goes through a puddle and splashes water up and that makes the outside of the bend shrink more than the inside and makes it want to open the bend up but it just puts a lot of stress on the tubes and eventually with some help from the infamous 4000rpm vibration the pipe cracks right next to the weld.
I have read here somewhere in the dim dark past something about tightening the bolts correctly but I cant find it as usual.
The red thing is getting sold soon as I get the K75 on the road so welding is probably the best option for now and hold it on with goanna tail string.

RicK G wrote:The thread title says it all.    Over the time I have had this K1100 the exhaust has cracked 3 times with 3 different exhaust systems. I have one left and if it cracks I will probably burn the damn thing.
I have been told that it is the mount at the gearbox and the tightening sequence of the 8 nuts at the head.
The first system was welded about 3 times and the next twice then a staintune from a K100 was put on and discarded because it was far too rowdy for me and then the third one cracked about 4 months ago. I have one good one left and don't want that also cracking.
All info will be gratefully accepted including voodoo and witchcraft but I draw the line at using chicken entrails to find the answer.

Rick,
A while back I was showing my garage find K11lt to a very well respected BMW engine specialist who was amazed at the general condition of my bike considering it had been stood since 1998.
He looked down at the exhaust and commented that the headers hadn't cracked near the collector-yet. He then went on to tell me that the Police bikes were always cracking their pipes and eventually cured it with a Jubilee (worm drive) clip around all four pipes to move the vibration away from this obvious weak point.



Worth a try?

Thanks Mike. After some examination of the current exhaust I decided to weld the crack and then put a band around the four pipes where the jubilee clamp is in that picture except I have welded the band. The other thing I decided to do is a mod of the rubber mount on the right side at the centre stand bolt. I made a slip in mount without much clearance from aluminium so it should support that side of the exhaust and not melt almost as soon as the heat is applied. It is the same mount as is used for the engine protection bars.
I will now be going on the Snowy ride and the 3500km trip will probably tell if what I have done will work.

Motorbike Mike wrote:Rick, cured it with a Jubilee (worm drive) clip around all four pipes to move the vibration away from this obvious weak point.



Worth a try?

Now that looks like a worthwhile and cheap preventative measure.  I might just do that on mine.  Won't hurt anything, and give a bit of voodoo peace of mind.

All the header pipes are the same length, so changing that is not a good idea. The hose clamp looks like a good idea. 
There is a business in Brisbane called "Motorcycle Exhaust Professionals" I used them about 10 years ago to manufacture a new muffler to replace my standard K100 muffler. I have no affiliation with them but the owner of the business back then was a genius. He was a kiwi that designed and manufactured the exhaust for the "Britton" race bike made in NZ many years ago. I didn't own a K11 back then but I remember him telling me that they always cracked where yours has and to solve the problem he modified the system to be a two piece system similar to the K100 where the muffler slips on. Might be worth a call to them.
My bike on the other hand has done 180,000km and the exhaust has never been off and has never cracked. I have wanted to take it off a few times but i'm not game enough knowing the history of them cracking.

Thanks for that Gary I will keep them in mind when I finally get to the 97 K1100 I have yet to restore.
I will be selling this one or parting it out.

perhaps temporarily fit up the laser noise device on the k100 pipes rick, then install ...like smithys new one. a rotatable silencer  (um washer like disk ?)

I once did this for the old duke with severely loud cigar shaped muffler (of sorts  ) ...made round town driving  quiet as a mouse ...but when needed  turned it 45 degrees for some little more ...erm oomph !

as you know the lengths of the headers on the k1100 exhaust, at the first weld point are very different ...ranging from 14 inches to 19 inches ... yes there might be some equal tune lengthening , which happens inside the large bulb that sits under the gearbox and the main silencer ...but by then any heat stretching and expansion is a dead loss to equalisation of the expansion of the pipes under load and environmental conditions


for the many that have had little issues , I'm forever a optimist ...but the science doesn't look right to me ...perhaps just a light touch is required in the sealing of the brass rings to the head ?  the restriction to this is the studs holding the retainers to the pipes ...perhaps drill out the stud holes in the retainers another 1mm or so to allow for "some " movement

sleave the pipes as they enter the muffler could be the long term solution ?

Take a walk down the street and fine one of them Vw's with the tweeting exhaust, flog the daffle from the back pipe and stik it on