What makes you think its valve seals? Is it smoking when you start it up? If not then the seals are fine. To replace the seals the head needs to come off. If you are that far you may as well hone or bore the top end and put new rings in.
Most often the valve noise you are hearing is the timing chain.
A service manual is a must if you plan on going this far. They are not to bad and worth every penny.
David
2008 Polaris RZR Lifted, Laws, Springs, Spacers, Snorkles (Sold)
07- Grizzly 700 29.5's on SS112's
06- Yamaha Rhino "Mi Lil Donkey" (Sold_
04- Bombardier 400 "Wild Thing" Paint Scheme (SOLD)
03- Yamaha Kodiak 450. Lawed. Piped, snorkled etc...
03- Arctic Cat 250. EDLs. Pipe, lift and snorkle coming soon.
04- Kazuma 110. Piped, snorkled, lawed etc.. The baddest of them all. lol (sold)