Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Snowbum says the "1980" on forward, so likely before the Sep 1981 '81 models. His article on the pulse-air system is here:
https://bmwmotorcycletech.info/pulseair.htm
So all the way up through the mid 90’s last variations, like the Mystic, RT and R100?
+1. The hotter exhaust valves was the reason I removed/blocked off the pulse air system in all my airheads (last one I took off was on a '94 Mystik). The combination of BMW's valve seat material change when unleaded fuel became mandatory* and the additional heat from the immediately adjacent fuel burn at the exhaust port resulted in accelerated valve recession. Removing the pulse air plumbing and rejetting away from EPA-mandated terribly lean Bings made for better running.but it does get the exhaust system and probably exhaust valves a bit hotter.
When in doubt, ask this man!I don't know specifically but it was for the 1981 models with the change to the valves. I presume then any bikes built September 1980-on. The issue as written by Oak was that the valve seats were made of tool steel which didn't transfer heat very well. The heat then was retained in the valve face. The valve face tuliped or warped more than recessing, but the result was the same. Oak used terms for valve recession prior to the 1981 models but for the 1981-1984 model years, he used the term valve face plastic deformation. For 1985, BMW finally got the metallurgy right.
* I can never remember the exact year the new valve seats came in. I remember BMW making a big deal of the new plasma-sprayed Nikasil cylinder liners when they came in in 1981, but I'm not sure whether the new valve seat material came in '80 or '81. There's getting to be too few memory cells left ...
Photo of ruined exhaust valve from my "84 R100RS ... compared to intake valve on left. That knife edge would soon fail, causing valve to retract far enough for keepers to separate and then valve to hit piston.
View attachment 96342
If I recall correctly, around 60K. Photo is from 2002How many miles were on the bike?