I have a 1988 Yamaha Inviter 300 single, minty little sled for the kids. Ran great up untill a few weeks ago when it started eating plugs...it goes through plugs like they are free. Will runn for about 30-45 mins and then the electrode onthe plug is gone! Not broken off or pounded but gone, like it has been eaten away like a welding rod.

Any thoughts on this?

stop driving it
i found a thing on the net about sparkplug tips
andi can't find it right now
have to go to work, by sled
i think it is predetonation or way too lean
i will google it when i get home tonight