The spark plugs are screw fastened in the flanks of the cylinder heads, near to the exhaust openings. Components required for spark plug replacement normally in a spark plug socket designed to fit a ratchet, different extensions and finally a spark plug gap checker which is used to measure the spark plug gap on the new spark plugs to be fitted. You need a plug wire removal tool, though it can be done manually, to remove the wire boots for spark plugs; torque wrench should be used for tightening new ones. There is much wisdom in buying spare plugs ahead of time, setting the gap to the right size and putting a new plug in as the old one is removed but to make sure that the correct sort of plug for the engine is used. It is recommended that the engine be allowed to cool before any plugs will be removed and also to check new plugs for defects and tightening the gaps. The gap is measured using the proper-thickness gauge which has to be place between the electrodes at the tip of the plug to slide with a little friction. To remove a spark plug wire, use pulling force only on the terminal end of rubber boot and if supplied then use the spark plug wire removal tool. If possible use compressed air blow out any dirt on the spark plug hole to minimize the chances of debris getting into the cylinder. Insert the spark plug socket over the plug and then retract it in anticlockwise direction in order to remove it-though the use of extensions if necessary. Check the conditions of its running by examining the old spark plug and put a thin layer of anti-seize compound to the threads of a new plug. Insert a new plug in a hole up to a point that one cannot turn it around with their hands as a final step, apply torque in the use of a wrench or a ratchet tool. When the plugs are inserted at the back of the engine it is possible to use a short rubber hose to help to screw in the plugs without straining the threads. Last, connect the plug wire to the new spark plug by twisting the boot and doing the same to the others in a cyclic manner, so that you do not connect the wires of each plug in a random manner.