Naraku Racing AC CDI with adjustable timing for customized tuning on 50 to 150cc GY6 engine based vehicles. The timing adjustment screw is set in the middle from the factory and has approximately 12 to 13 turns in either direction to advance or retard the timing. The screw clicks into place at each setting. Please note: This is only compatible with AC charging systems. Please confirm plug connection is correct for your vehicle. Please see our Warranty & Returns Policy.