we are presently using BR8es plugs which the manual calls for, yes we have tried more plugs, no the electrode isn't being damaged, no we don't use it for a long period of time, one small 5 minute run then shutting it off can do it, can't start it again because of damaged plug. We also know of a KDX 80 motorbike that did exactly the same thing. Would ratio mix of fuel have anything to do with it? Thanks