I don't have a reliable explanation for the greater seat width you have found on your inlet valve. The seat width increase is associated with "valve recession": the valve works its way deeper into the seat over time due to wear on both valve and seat, hence you have to adjust the tappets annually. Generally, because exhaust valves run much hotter than inlet valves, and because they are smaller diameter and therefore have less seating contact area, it is exhaust valves that suffer the worst recession and seating width increase. However engine manufacturers use a harder material for the exhaust valve, and sometimes also for its seat insert, to prevent this from happening. In the end, either valve may recede more, you can't tell until you test it.
Post-edit: The GXV120, and the rest of its engine family, have extremely hard exhaust valve seat inserts. Honda specifies a diamond cutter for re-cutting them. I made an attempt on one with a normal Warren and Brown hardened cutter, and made no impression at all - had to resharpen the cutter, too. The inlet seat in the same cylinder head was very easily recut with the same W&B cutter, it behaved like ordinary cast iron.
Sounds as if your mower is an HRU194, and it hasn't done an enormous amount of work. It may need new piston rings - you will find out when you check the ring gaps.
Last edited by grumpy; 21/10/13 02:01 AM. Reason: Add post-edit
