Learning

This post will explain some of the things I have learned in this project.

the spark plug ignites the compressed air fuel mixture in a cylinder. It threads into the top of the cylinder, and uses a powerful electric spark, arking through the small gap at the tip of the plug to initiate combustion. Diesel motors do not have spark plugs,this is because the diesel air mixture in a diesel engine auto-combusts under the higher compression in the cylinders. Different spark plugs have different heat ratings that indicate how intense of a spark it can allow. The more intense the spark, the better the air fuel mixture will burn, resulting in a smoother more powerful motor. Running to hot of a spark can potentially damage the ignition system. the heat rating of my spark plug according to the owners manual is 9h.

The carburetor, in the simplest of terms, provides the motor with the correct mixture of air and gas. I decided not to take it apart and clean it, because the carb is fairly complicated, especially with the electric throttle position sensor. Instead I poured a healthy amount of sea-foam engine cleaner into the gas. Sea Foam can help clean the carburetor and motor when burned in the gas. I also learned that it is  important to run octane boosted premium gas in motocross engines, to keep the motor clean, and to get optimal performance.

My quads carburetor is a 38 millimeter (inner diameter)  of . The carburetor is located in between the air box (right) and cylinder (left) as the motor draws in air from the air box during the intake stroke, the air is pulled through the carb where it is mixed with a small amount of fuel. The black hose connecting to the carb is the fuel line from the gas tank, it fills the float bowl (bottom of carburetor) with gas. The gas in the float bowl pushes a float, which allows gas up through several needles, there are several needles or jets, the 2 important ones are the idle jet, and the main (pilot)jet. The idle jet always allows squirts up a small amount of gas, regardless of throttle position allowing the motor to idle. the main jet allows more fuel into the air stream depending on the throttle valve position, ie you twist the throttle, and it allows more gas into the cylinder. The throttle also opens a large valve in the carburetor that controls air flow, the more throttle input, the wider the valve opens and the more fuel and air is drawn into the cylinder.

The top photo is a view of the throttle valve, the slight opening at the bottom is always open, it allows a small amount of air for the motor while its idling. 

 The air and fuel mixture does not need to be forced into the motor, the natural vacuum pressure caused by the piston going down draws the mixture through the intake valves with sufficient force. A A turbo charged or super charged motor forces more air into the cylinder than would naturally be drawn in under vacuum pressure. great deal of force  in and into the air flowing through the  carburetor. The orange hoses are overflow hoses, that allow excess gas to drain from the carburetor.