My K1100 is dead in the water for the time being but I have been offered a K100 at a very reasonable cost.  My question is this - is it possible to put a K100 engine into a K1100 frame or vice versa and if so what are the likely pitfalls one might encounter ? I look forward to members thoughts on this subject

Physicaly they fit just fine but (and there is always a but) the question of which ECU to use will arise.
Using a motronic will tend to run a bit rich but that is not unsurmountable. Some tweaking with the TPS and CO2 adjustment should see it ok. Using the LJetronic will need a change of much of the engine gear and ECU from a K100 to be installed.
Personal choice for me would be the Motronic ECU and use the K1100 injectors into the K100 fuel rail and K1100 throttle bodies.  And dont forget to ust the K1100 temp sensor from the coolant outlet actually you will need to use the outlet stub as well.

Thanks for the informative reply Rick G - not quite as straightforward as I had hoped.  Maybe I should just forget the K1100 and resurrect the offered K100 so that I have two to choose from.  In which case, parts may be available from the K1100LT if I part it out or I would be willing to sell it in one piece to someone that has the time/knowledge required to repair it.  It is a very tidy 1993 model in KaricBlau with ABS etc.  Everything functions as BMW intended and all bodywork etc. is also in good order.

Any thoughts folks ?

I believe the chassis and suspension system is superior on the k1100 , not counting the rear end etc

as rick said a number of things to do to the 100 motor to make it worth while
but I don't see any issue really ...all the intake stuff ...water riser and electronics that needs to get changed over would be pretty easy as you would have most of it stripped for the change over .
definitely an advantage with the k1100 tb's
if you could get a good motor and for the right price ...why not ?   or is it a time convenience thing ?

krambo wrote:Thanks for the informative reply Rick G - not quite as straightforward as I had hoped.  Maybe I should just forget the K1100 and resurrect the offered K100 so that I have two to choose from.  In which case, parts may be available from the K1100LT if I part it out or I would be willing to sell it in one piece to someone that has the time/knowledge required to repair it.  It is a very tidy 1993 model in KaricBlau with ABS etc.  Everything functions as BMW intended and all bodywork etc. is also in good order.

Any thoughts folks ?

If you like the 1100LT and it's in good nick, hang on to it, a donor bike will pop-up at the right price.

The one that's on it's way to me has 50,000 miles on it and is apparently the opposite of yours: the fairing is damaged, the screen motor has failed, the rear brake has no pressure and the ABS has been removed. I've paid 500 quid for it including delivery from Nottingham.

Let's be honest, the RT/LT is the least valued model in the UK (that's not to say that it deserves to be so under-rated) and the prices are currently at rock bottom - I've seen a couple of really clean, very tidy low mileage K1100LTs go for about a Grand on ebay in the last twelve months. 

If you have the room for it, remove the engine, see if any of the Mini types want the head and wait for a donor bike to pop-up.

Thanks for the reply MikeP.  I have room to store the K1100 in the dry for now so maybe I will hang on and see what turns up. Bike prices are generally lower in the winter months so who knows what might turn up.  Thanks again for taking the time to reply

Well, I just discovered a crack in the front motor mount on my "new" '91 k100rs 4v (the mount on the head).  Now, I'm weighing my options on a fix and it appears the good folks in this post may have some valuable info (Rick G?... seems to know quite a bit!!).  My first thought was to put a new head and gasket on the bike but then I thought....

Why not put a low mileage k1100 engine into the bike?  If I go that route, what else would I need to swap over?  Should I also mount the k1100 throttle bodies?  I think the electrics should swap over just fine, but I thought I'd let the folks here chime in.

Also, looking at the heads, the k1100 and k100 4v heads appear to be the same with the same part number.  Am I correct on that?

Right now, I am leaning toward swapping an entire low mileage k1100 engine if it is a straight ahead swap.  After reading through a number of forum posts I understand I may get a little more mid range umph out of the bike.   Sounds good to me.

Any info would be MUCH appreciated!!!!

Thanks guys!!

I would use the K1100 TBs and you need to use the K1100 FI rail because the K100 has the injectors directly into the head and the K1100 has the injectors in the manifold stubs but use the K100 injectors and L Jetronic ECU that comes with a K100 and the water outlet stub on the cylinder head needs to be changed but retain the original temp sensor from the K100. Also you will need to use the Throttle Position Sensor from the K100, to do that use the shaft from the rear TB of the K100 TBs  to make the TPS work. You can go without a TPS there are a few here who disconnect them
Other than that nothing I can think of.

He's got a K100 16v Rick - K1100 has the same injector set-up (into the TBs).

MikeP wrote:He's got a K100 16v Rick - K1100 has the same injector set-up (into the TBs).

Oh DOH:bh:

RicK G wrote:

MikeP wrote:He's got a K100 16v Rick - K1100 has the same injector set-up (into the TBs).

Oh DOH:bh:

Hi guys and thanks for the replies!!  Yes, MikeP is correct, this is the 16 valve engine with the injectors in the manifolds.  I went and double checked last night.  So... I'm thinking the k1100 engine with my k100 16 valve manifolds and the throttle bodies from the k1100.  I'll use the injectors from the k100 and the tps from the k100.  My understanding is the cams are a little different between the motors but that they have the same timing and the ecu from the k100 should still work.  Other than that I think it should be a pretty straight forward swap.  Fingers are crossed.  Any other thoughts are much appreciated.  I'll let you know how the swap goes as I gather the necessaries at the shop.

cheers!!!