Baja Ron offers (https://www.spyderlovers.com/forums/...rs-amp-Helmets) and most people use the NGK CR7EIX Iridium which has a thread diameter of 10mm https://www.sparkplug-crossreference...eter%3A%2010mmThose bolts will not fit down into the hole. The spark plug holes are less than 8mm and the bolts are much larger than that.