Can both the intake and exhaust valves be lapped? I'm reading that some valves are case hardened and should not be lapped. Cannot seem to find the info on the 250 valves. Blew a head gasket, so I figure while I'm in there I will attempt my first ever valve job. Purchased the gasket, but am wondering if I can use the stock valves or if I need to buy new ones. Any additional advice appreciated.On a side note, I've been told I have a "stuck intake valve" on my EX500 so I'm into the same process for that bike and found that the exhaust valves can be lapped, but the intake valves are case hardened and you should not lap an old (used) case hardened valve, as it will quickly wear through the hardening. Is the majority in agreement with this?