I posted two photos of the head off my engine at:
There is an incrediable amount of buildup on the exhaust
valves for an head that only has 5-6 thousand miles on it.
The rattling sound that we thought was either a loose
seat or a bad bigend bearing was actually the crud on the
backside of exhaust valve #4 hitting the air injector.
If anyone has any ideas on how to avoid or lessen this
buildup I'd appreciate hearing from them. Maybe a
different gas or spark plug? There are more details
on that page as to the gas I've been using, etc.