Motorcycle Repair: Valve lapping, american honda motor, honda ct70

Question
In a rebuild manual I have, it says not to grind or lap the valves for my 1971 Honda CT70.  Why is that?  Are the seats or the valves coated with a special metal of low thickness?

Thanks

Answer
SL #84 5/4/71

INTAKE AND EXHAUST VALVE REFACING - NOT RECOMMENDED

The intake and exhaust valves in some Honda engines have a bimetal head and stem. A hard stellite facing is welded to the valve face and the end of the valve stem to provide a long wearing surface. This hard surface is thin and can be destroyed if the valves are ground. If a valve is burnt, warped, or worn excessively, replace the valve; do not attempt regrinding the valve face or stem.

On the other hand, the intake and exhaust valve seats in the cylinder head can be recut as often as necessary, provided the valve seat still makes contact with the center of the valve face. Refer to the applicable shop manual for valve seat width specifications.

When installing a new valve in a used cylinder head, the valve seat should be recut and the valve lapped to the seat, to obtain a perfect seal.

     AMERICAN HONDA MOTOR CO., INC.
  9-725      Motorcycle Service Department
---------------------------------------------------------

I think that covers your question....  Bill Silver