I have a N42 head that I sent out for some head work, but during shipping, an exhaust valve was bent. I have a spare L20B head in my garage and the numbers for the exhaust valves match what is listed for the N42. Both the L28 and L20B list 35mm diameter and 116mm length in the "How to Rebuild" book.
Can anyone confirm that these valves are interchangeable? Thanks!