In this category you will find all the ignition coils we can have for your YAMAHA 4 stroke motocross like YZF, WRF, ...We will propose you only original quality products or better at the best price. How to know if a coil is tired ? You have to take a voltmeter and measure in OHMS. To know which measure corresponds to your motorcycle for that it is then necessary this inform on the technical review. If the measurement is OK, you have to redo the measurement when hot and check again. If everything is OK hot or cold, the problem is your ignition, spark plug or other.