Blow Air before Spark Plug Removal. This is the Only Way to Avoid Plug Thread Hole Problems!

Prevent problems with threads and combustion chambers by simply blowing on the plug holes with an air blow gun.

Check the threads of the removed plug for damage and that the gasket is crushed on average all the way around. If part of the cylinder head side of the gasket is pitted, check the bottom of the plug hole, as a foreign object may have been chewed between it and the head.

Therefore, I would highly recommend air-blowing the plug holes, which is done before removing the plugs. Pebbles and gravel are often dried by the heat around the combustion chamber, so they are easily blown away by air blowing. If the bike has been stored outdoors for a long period of time, rainwater may collect in the plug holes, which will also be blown out like a fountain by air blowing.
The same goes for engine oil. If water or oil has accumulated, you want to visually check the condition of the plug holes in addition to air blowing, so you will have to add the effort of removing the gas tank and air cleaner case, but once dry dust and grit are no longer spewing up, you can insert the plug socket and remove the plug. An air compressor is required to use the air blow gun, but if you do not have a compressor, you can use compressed air from a bicycle inflator. An air supply that comes with an attachment that can be attached to the end of a hose can be used to achieve the same effect as an air blow gun.

If you air-blowed the plug holes before removing the plugs, you may be tempted to air-blow them before installing them, but this requires caution. If you blow air after removing the plug, dust, and gravel left near the plug washer may wind up and get caught on the cylinder head threads, or they may adhere to the contact surface of the plug washer and get caught when tightening the plug. If there is a foreign object on the threads, you will notice discomforts such as a scratch or reluctance when tightening the plug by hand, but if a foreign object is caught in the washer, the screw itself turns smoothly and can be tightened, so it is difficult to notice anything wrong, and even if the tightening torque is reached, the cylinder head and plug are not tightly connected, This can lead to a situation where the cylinder head and plug do not adhere to each other even if the tightening torque is reached.
Ideally, after removing the plugs, it would be ideal to wipe the tightening seat surface of the cylinder head with a rag sprayed with parts cleaner to remove any dirt. If you have to remove several parts above the cylinder head to do so, it is safe to refrain from blowing air after removing the plugs.
Although it is somewhat delicate, plug-hole air blowing before removing the plugs has only advantages, so be sure to practice it.