Hello everyone,
my name is Marten and I live near Santa Barbara in California.
Two years ago I restored an old Airhead boxer and enjoyed the work very much.
Two month ago I came across a basketcase of a 86 K100RS and decided to take the challenge.
Beside the overall rough shape the engine has low compression but started after I fixed the clutch switch.
I found an replacement engine on e bay for a good price. It is from a 89 rs with 23K miles. Now I want to make sure if the model and year of the engine is as advertised.
I noticed that that the wires coming out of the Hallsensor/ignition trigger assembly are different between the two engines and can not find it on any of the wiring diagramms .
So the head scratching begins...

Marten

good luck marten

sounds like you have bits of 2 different generations of the k

the new motor sounds like a 16 valve version ...whereas the 86 would have been a 8 valve version ...so there might be some differences in the electrics , connections, air path ...just to start with ...

hmm i wonder if you could fit all the old engine accessories to the 16 valve .....yeah its kinda a backward step ...but might sorta work

Hi Marten a belated welcome to the forum. When you say that they are different a bit more info will help.
The wires that come from the hall sensor should be red + Black - and an orange and brown are signal wires. There will also be an extra one or two wires which come from the oil pressure switch which should be a brown with green trace and the other I can't find reference to but will be a sender for a temperature gauge that was optional on the RS.
The last 2 wires will go straight through the hall sensor cover and across the top of the water pump and down through a hole in the casting to the two switches at the bottom of the oil/water pump.

The engines are quickly identified by the spark plug cover which will have 4 valve on it or just BMW for the 2v engine.
The 4v engine could be used but you would need to change some sensors.
Best to check it out first but from what I can find any 1989 RS from US would be a 4v engine or 16v as some call them.

Hi and welcome Marten, sounds like you have a challenge on hand but I am sure a lot of info and help can be found on this forum.

BIG D

Welcome to the board Marten! Take a pic or two if you get an opportunity?

OG

Welcome to the forum. Sounds like you have set yourself a bit of a challenge. The two valve machines had slight variations as time went on, especially 83-86/86-91. Good luck with your project.

Welcome Marten and good luck with your project. Post up some pics as you go if you get a chance.

Thank you all for the warm welcome!

16 Valves?! Ooops!

Just for giggles I bid on a 89 K100RS engine on ebay.
Next day I got it for $99 !
I knew from someone here that in 89 the output shaft is better, but it didn't occur to me that it could be a 4valve engine.

Well for that price!
The side, front covers and bellhousing on my 86 engine were at one time chromed and now are peeling the chrome off with some heavy corrosion underneath.
If I could just use the very nice covers from the 89 engine I have my money worth.

Today I opened the Timing cover and NO trigger assembly!
That's why there are only two wires coming out, the ones from the oil/water pump.

There is also no valve cover to indicate the 4 valve.

I will post a question in the General discussion section on how to fit a 89 engine into a 86 bike.

Thank you everyone

Marten

great price all the same marten ....yippee

The Spark plug cover where the 4Valve is written if it is a 4v then there are 4 x 6mm screws to hold the cover and the 2v only has 3 x 6mm screws.
I am not sure about the Crankcase cover but the valve covers are not interchangeable.

Welcome aboard Marten.
Regards,
K-BIKE

Thank you everyone and K Freak for your help.
I checked today and the 89 engine has 3 ! bolt holes to fasten the sparkplug cover. That would make it a 2 valve after all. Did they still made 2 valve K bikes in 89?


Marten

It was only the K100RS that was a 4v the K100LT was a 2v up till end of production in 1991.

phew !!!.. thats a relief then marten

swap over the bits and then ride ....woohooo

but beware of all those crumbly rubbers ...good luck mate

K Freak, so BMW produced 2 and 4 valve , side by side till 91. I understood that they all went to 4 valve not long after the K!. It would have interesting on the production line.

ainsjac wrote:K Freak, so BMW produced 2 and 4 valve , side by side till 91. I understood that they all went to 4 valve not long after the K!. It would have interesting on the production line.

Just running 2 seperate lines and despite the looks the 4v are a very different bike. There isn't a lot that is interchangeable without knowing it has been done.