I have a 2004 RM 125, that miss fires really bad when under load. Almost like as if the plug is starting to fail. I have changed the plug but still cuts out really bad. standing still with no load the bike revs up into the higher rpm but starts to miss a little towards the top end. When climbing a hill and the power is needed the bike starts to cut out and all power is lost. Clearing the cylinder before a climbs doesn't seem help. Any suggestions?