What is main jet and pilot jet?
The main jet controls the amount of fuel when you’re at about 80% to a wide-open throttle. The pilot jet controls the fuel level when you’re at idle to roughly 20% throttle. The jet needle controls the fuel level when you’re between 20% and 80% throttle.
When should I increase my main jet size?
Jet Sizing When the Temperature Changes This creates a lean condition that runs the engine hotter, ideal for cold conditions. If the air temp raises above 105 degrees, larger jets will be needed to increase the amount of fuel entering the combustion chamber, known as a “rich” condition.
What happens if main jet is too small?
Be careful: most engine jams occur when the main jet is too small. A lean fuel/air mixture will cause the engine to overheat fast.
Does main jet effect idle?
main jet has no effect on idle. you can remove the main jet completely and it will still idle just like it did.
Is it better to run rich or lean?
TLDR – running just a little lean could improve fuel economy and give extra power. However, run too lean and you risk engine failure because the engine runs too hot. Whereas running rich can waste fuel and increase pollution but will not damage the engine.
Where is main jet on carburetor?
The main jet is located at the bottom of the carburetor inside the float bowl. It’s the larger of the two jets, and it is installed in the needle jet—that part we will be covering next week.
How do I know what size main jet to buy?
The suggested change in jet size is to go down one jet size for every 1,500 feet in density altitude you go up. Conversely, for every 1,500 feet you go down in density altitude, go up one jet size.
How do I know if my main jet is too lean?
The most common symptoms of lean jetting in a dirt bike are:
- Hard to start when cold.
- High idle.
- Hanging idle.
- Abrupt throttle response.
- Engine overheats more easily.
- Bogs when accelerating.
- Bike is running worse at lower elevation.
Does main jet effect starting?
The main jet does not effect the jetting for starting and idling. It plays no part on low RPM or mid RPM jetting either. The main jet is very important to your machines overall tuning, but should never be over emphasized at the expense of needle tuning or other facets of your carburetion tuning.