Here's a nice example of guide wear for you. Mouse over it to see the amount of slop.
valve face
valve profile
This was on a 1989 R100GS with 52,000 miles. Pulse air system in place. You can see the face of the valve beginning to crack; here are two better pictures of the valve itself. Click for close-ups.

Valve sizes

Engine 27 29 31 32 34 36 38 40 42 44 Guide
R50/5       EX IN           8
R69S, R60         EX   IN      
R75, R80             EX   IN  
R90               EX IN  
R100 early               EX   IN
R100 late               EX30° IN  
R50, 60/2       EX IN           7
R65 early         EX   IN      
R65 late           EX   IN    
R1100 to 10/95     EX30°     IN         6
R850 EX     IN             5
R11xx 10/95-on   EX     IN          
R1200     EX     IN