Dropped Exhaust Valves

[raypond]

G'day Gordon, I broke a valve on my '86 R65 at 170,000km. I believe them to have been the original valves. What apparently caused the valve to break was the wildly excessive wear in the guides allowing the valve heads to seat unevenly. The valves did rattle a lot before it broke. Cheers, Ray

[Rob Valdez 79 R65]

Yes - Bob Grauer is VERY good!  Just Google Bob Grauer BMW to find his phone #.  He is in the San Francisco area.

[Gordons_HQ]

Thanks everybody who have contibuted here, from what I can gather from the answers it seems a definite problem and prevention by fitting new exhaust valves seems a good idea. So I guess I had better start saving the pennies.

Cheers,
           Gordon

[Rob Valdez 79 R65]

Thanks everybody who have contibuted here, from what I can gather from the answers it seems a definite problem and prevention by fitting new exhaust valves seems a good idea. So I guess I had better start saving the pennies.

Cheers,
           Gordon

Standard procedure is to replace the guides, as well, and measure the springs for tolerance.
Most people check their cylinder bores for "roundness" (less important in '81-on engines) and ring tolerance at the same time as the valves.  Thus called a "top end rebuild".

[Bob_Roller]

Gordon, what year bike do you have ?

The '81-83 year bikes had problems with valve recession, '81 being the worst year of all of the bikes, this was across the entire BMW motorcycle line up the 800 and 1000 cc bikes as well .

If you decide to have the work done, make sure the valve seats are replaced, as they are the real problem in this matter .