Valve recession myth or fact?????

[scottyintex]

I just read an article that said the valve recession problems of the 1980-1984 BMW’s...due to the dropping of lead as an additive in gas....is now showing up in all the /5, /6, /7 bikes... and R65's The lead no longer being there to lubricate and cool the valve seat surface. That as the last residual lead wears off.........problems will start cropping up sooner or later. Ok.........is this some dooms day prediction.....like the world will end in 2012. Or........... is there some thing to this. I think something along this line has cropped up in one of the threads but I can’t find it. Anyway....will someone with some mechanical knowledge enlighten me on this issue. What does a top end repair job cost these days?

[Rob Valdez 79 R65]

I don't' have mechanical knowledge that you can depend on.

I can tell you to watch your valves regularly to see if the gap is closing up.

My valve job cost a little over $500, but I went for overkill and had the intake valves replaced.  Probably not necessary.
I knew mine needed done when I pulled in to a rest stop and my bike died.  It would not idle.  It ran fine at speed.

The next morning, at my destination, I adjusted my valves (left exhaust, NO gap).
When I got home, 450 miles later, that valve had closed up, again.


This is not a conspiracy theory.  

Could it be possible a previous owner already had hardened seats put in?

[Bob_Roller]

The problem started with the '81 model year bikes .

BMW started using a new alloy for the valve seats .

They didn't know, that this alloy acted like an insulator, preventing the valve to transfer heat to the valve seat then onto the cylinder head .

This over heated the valve, and caused valve face plastic deformation, that's the technical term for it .

I have an '81 R65, original owner, and at 45,000 miles, I stripped the threads off of the exhaust 'spigot', I took a look at the valve faces in the open exhaust ports, and the valves were extremely worn, the metal had 'flowed' towards the valve stem .

I had a 'top end' overhaul done along with the exhaust thread repair .