Curtis, I am curious about these exhaust valves, it would be good to get some information back from the machine shop as to the material and technology used in the valves. Reason being, BMW states lapping or valve replacement, which may mean the valves are nitrided, which typically can be as thin as 0.0005" and a light lapping does not adversely affect that coating, whereas re-grinding will. Also, regarding the valve seat geometry on the exhaust side, is the information available regarding seat width, angle etc ? I think cylinder heads on these engines are typically very good in this area, as not too much is written about problems.
Dennis, good questions.
Stopped by my local BMW shop and talked about grinding my exhaust valves. They have a local machine shop that they work with. Apparently, they do grind the valves on K bike engines.
Here's a cut n' paste from AJ Cycle's website:
"AJ Cycles Services
Full Service BMW & MOTO GUZZI dealer. Certified Master mechanic with 38 years motorcycle experience.
Parts and Sales personnel with 48 years motorcycle experience.
We have excellent machine shop services which include: Welding (Fin Replacement, Crack Repair in Cylinder Heads, or General Repairs), Boring, Valve guide and Valve seat replacement.Vacuum Testing. Valve Jobs
If it needs to be machined, we can do it all with state of the art equipment."
So at this point, my head and valves are going to the machinist for his evaluation and comments. We shall see what he recommends/does.
Also of note is the official BMW Service Manual states that if the valve seat is ground, new valves should be ground in. Hmmm....what does that mean?
Also, the gent (Alan) at the BMW shop repeated something DShealey posted above, which was that lapping was an "outdated" procedure.
When I said the BMW Service Manual mentioned lapping, the gent at the BMW shop questioned me: "Are you sure that BMW says that?". So I went back and looked; actually the BMW Service Manual does not mention lapping. BMW simply states three things regarding servicing the valves:
1) "Machine the valve seat with turning tool BMW No. 00 3 530.",
2) "When remachining, the correct width of the valve seat must always be maintained.",
3) and "NOTE: If the valve seat has been machined, install and grind in new valve."
The Clymer manual has a more extensive section on valves and does discuss lapping. But then Clymer could just be adding generic, general info on customary valve procedures which are not really BMW specific.