Join Date: Sep 2006
Location: Austin, Texas, USA
I did this swap 17 years and 50,000 miles ago so remembering the details is sketchy. The stock or aftermarket exhaust will still bolt up to the head just fine. The 4-valve design moves the exhaust ports ahead maybe 10mm,3/8 in. the rear mounting is slightly affected. I bought a complete K11 engine, airbox, Motronic computer, O2 sensor and engine wiring loom out of a junkyard for less than $1000- less than I would have spent on rebuilding the original engine.
The hardest task was modifying the '85 wiring harness to power the Motronic system. I remember spending the winter with this project. I took several sets of '85 and '93 wiring diagrams to map out each part of the separate systems to cross over. I remember having trouble with fuses blowing when winding out (hard accelerating) the engine. A whole series of dedicated grounds and increased capacity fuses finally fixed that.
Was it worth it? Riding the bike after made me feel that this is the engine that should have come with the bike to begin with. Better torque all the time. Within the last couple of years I went through the bike mechanically and cosmetically and it looks and runs like a new one- but it is still a 30+ year old scooter and feels like it compared to my '16 R1200RS. I really don't like riding it much anymore. But I'm keeping it since it really isn't worth much to anyone but me.
Good luck with your project!
'17 R1200RS, 2 yrs. 27,000 mi.
'16 R1200RS, 18 mo. 28,000 mi. (gone)
'03 R1100S Boxer Cup Replika 6/200
'85 K100/1100RS, 34 yrs. 326,000 mi.
'05 R1200ST, 8 yrs. 57,400 mi.-3rd deer killed it.
'11 R1200RT, 2 yrs. 30,000 mi. (gone)
'99 R1100S, 2 yrs. 15,000 mi. (gone)
'96 Ducati 900SS/SP, 12 yrs. (gone)
500,000+ BMW miles