For all carburator-equipped, non-EFI motorcycle engines, knowing how to read your spark plug can mean the difference between a well-maintained engine and one that will have a lot of problems down the road.
Because carburetors are basically manually set, over time and the constant vibration, the settings will gradually change from what is known as optimal, where the fuel and air mix in the combustion chamber is at its sweet spot and barely leaves residue. This is what you read at tip of a spark plug.
And by saying “read” we actually mean knowing how a spark plug should look after you take it out of the engine and inspect the firing end.
There are actually three common states for sparkplugs that have visual cues when you know what to look for.
OPTIMAL carb setting is when the engine performs well on first start after being left off overnight, which is known as cold state. After running it for about 200 meters, remove the sparkplug and let it cool. Then look at the tip that goes into the engine. If the inner part appears white; that contact point in the middle of the white part is not too black and that metal part extending over it does not look too brown, then you have an optimum carb setting. That means your carb is mixing air and burning fuel efficiently and there is not oil spillage.
RICH carb setting is opposite of the optimal state, the inner part of the spark plug is nearly all blacked, even the metal part extending over the contact point. The outer ring might also appear to be damp. This is known as the rich carb setting and means that more fuel is coming in than air, which is not burnt by the sparkplug during combustion. This also means that you are burning too much oil. And, if there is dampness anywhere on the sparkplug, there could also be a possible oil leak coming into sparkplug.
LEAN carb setting is visually seen as brownish color over all the inner parts of the sparkplug. This means that the air is higher than the fuel in the cylinder, causing the explosion to become too hot. This heat build-up, if left unchecked, can cause a lot of problems internally and should be addressed immediately.
So what do you do? If you read your spark plug as being too rich or too lean and you are not a trained mechanic – dont mess around with it. Bring it directly to your trusted 3S shop and get your carb setting fixed by an expertly trained mechanic who will know exactly how to find the optimal “sweet spot.”
Caring for your motorcycle always begins with you and your attention to details. Motocare is taking care of your ride so that it can also take care of you, kaibigan.