I now have about 200 miles on the new TR250. Doing a little carb adjusting, the engine is missing at higher rpm's. So I keep playing with the mikuni carb's. I have never worked with them before. I could not get rid of the miss. I decided to check spark, turn's out there was a bad spark plug. This is the second time this has happened on this car. I replaced all the plugs with new ones and the car runs great. How often do spark plugs go bad? Can the coil fry a plug?