Hi

I have the top box shown in this image. First I am looking for a reference to it's construction. We are changing the colour of the bike and it would be useful to remove the built in back rest for a neater spray job. So if anyone knows how to remove the back rest, help will be much appreciated.


My second question is around attachment. The box was directly attached to the tail piece on the bike that bought. This feels a little less than secure. The mounting kits shown on realoem for the 34l top box, does not seem to match this box. So how should the box be attached safely? 

That looks like a K1100LT top box.

If so you need the carrier below [Motorworks below] but this suits the 35 litre and the bigger 42 litre one. There is no mounting plate required. The latch mechanism on the rear of the top box secures it to the rear cross rail on the carrier. It comes flat pack and bolts together with Allen bolts. The two side rails can break but they can be bought separately, I needed one for my K1100LT when I got it.

Used - 35 Litre top case fitting kit | ACK16220 Close X Fits K75RT, K100RT, K100LT/ K1100LT Associated BMW part: 46545316220 (46 54 5 316 220)
Larger Image	Original equipment luggage rack comprising the two large side struts and the four central cross pieces. This rack allows fitting of the 35 Litre BMW top case, ACK16287 . It is listed for RT and LT models by BMW, but can be fitted to all other K75, 100 and 1100 models too.	£65.00 No VAT payable Stock of this item varies daily. Please call to check availability and condition

I will take some better pictures of the box and post them. It has two latches, keyed to the same keys as the side cases with a similar design. 4 Mounting screws in the bottom. Two of which are moulded studs and two are bolts. They line up with the supports in the tail piece and that is how it was installed on the bike I bought.

That sounds a different box then, the K1100 has only one lock.

K1100 ones are good but not cheap.

Finally got around to taking some pictures of the box after it's return. I am still slightly puzzled as to it's mounting. The bike I got it from was a late 80s K100LT (claiming to be) that had the box affixed directly to tail piece. The part number reference draws a blank on realoem.

Finally found one German thread discussing the box. I am no wiser between my almost non existent German and Google translate,

https://www.reflex.at/~pezi/3/1844503.htm

So it seems to be a 50l top box, known to shear it's mountings....... scary.

92KK 84WW Olaf wrote:That sounds a different box then, the K1100 has only one lock.

K1100 ones are good but not cheap.

But the mounting rack for the K1100LT 35L top case is crappy. It's plastic and the case wobbles while riding.  That K1100LT plastic rack also has a propensity to crack so it's a good idea not to put much weight in the 35L top case.

That is an original trunk from a K100LT.  I bought new and still own a 91 K100LT which came with a trunk like the one you have.  The original mounting does not mount to the tail piece but to four separate brackets mounted to the rear subframe of the bike.  I will try to take some pictures for you sometime today but no promises.

That would be awesome. The 91 reference is also useful, I may find something by looking through that model's options.

It shows up in the 1991 US sales brochure.  Is there an 11 digit BMW part number cast into the base or lid?

I have the dealer ETK parts software from 2001 (which often helps me find old part numbers) and it doesn't show up there for a K100LT.

It was my understanding at the time that I bought the bike that BMW of North America are responsible for installing that trunk on the bike after it got here in the US.  My bike also came with a Corbin seat on it.  The seat had a label on it that said "BMW by Corbin" on it. I was able to find a parts list for the trunk brackets one time but I can't remember where.

Could it be a Siebenrock?

They did a 50L top box that sits on the original k100 rack and plate?

[url=https://servimg.com/view/19311229/15]
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Now that is a mounting system I would trust and gives me some ideas as to how to make a mounting system. This box has no holes in it for mountings, except for the 2 studs and 2 bolts that pass through the bottom of the box and fits through the tail piece. The tail piece has 4 reinforced spots, that seems to be molded for mounting bolts.

The part number sticker in the lid is partially worn away. The digits match the number in the base. 




The second picture is of the BMW warning label, which makes me smile a little. 130 km/h is at the lower end of the highway cruising speeds that may occasionally occur.

The final picture is of the two exposed mounting bolts in the box. The other two mounts are studs. These pass through the tail piece. The bike this was mounted on, had had simple rubber washers between the tail piece and the box, and large round washers inside the tail piece with nylon lock nuts. The absence of further mounting holes makes it look like this box was never mounted in the way Kioolt's box was mounted.

This could very well have been BMW South Africa coming up with interesting solutions to fitting the box as an aftermarket feature without making new holes in the Tail Piece.

The tail piece had the mounting spots for four holes long before the K100LT came out so I think it's safe to assume that those were designed to hold the tail rack for the 22L top case, not the much larger K100LT top case so the additional metal tubes to mount the larger top case to the frame make more sense - like the pics that kioolt posted.

Also, when loading up a bike it will generally handle better when heavier loads are lower and farther forward.  I only put lighter stuff in my top cases.

Agreed.
The challenge would be to either find a set of original supports, or have an engineering shop make new ones.

The box is very convenient, fitting two full face helmets.