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.
What do pilot jet numbers mean?
For example, a jet may be stamped (on its head) with the number 30. This indicates that the jet’s size is 30 mm. Installing a smaller size jet will reduce fuel flow, which is ideal for high-altitude conditions where air is limited, where a larger jet size increases fuel flow for oxygen-rich, low altitudes.
What does the pilot jet do in a carburetor?
The pilot jet handles the mixture from idle to 15 to 20 percent throttle. Air comes in through the front of the carburetor drawing fuel up through the pilot with a vacuum that is created as the air flows through the pilot circuit.
Which is the best jetting jet for a bike?
Here is a table made from the formula: So lets say you take your bike and put on a new pipe, airbox, and such and get it jetted well in Denver on a 60 degree day (CF=.963). Lets say the main jet that runs best is a 180. Your new STP main jet is a 180/.963 = 187.
What’s the correct size for a pilot jet?
The pilot jet is sized correctly if the fuel screw setting falls between 2.5-3 turns out. The pilot jet is sized correctly if the air screw setting falls between 1-2 turns out, with 1.5 being the sweet spot.
What kind of jet do I need for a 34pict / 3 engine?
Assuming a vacuum distributor, the 34PICT/3 carburetor is usually jetted with a X127.5 main jet, and 100Z -120Z air correction jet. For the 1600cc engine, you need more fuel flow, so a larger X127.5 main jet and 100Z or 120Z air correction jet are needed.
What kind of jet do I need for a 1600cc engine?
For the 1600cc engine, you need more fuel flow, so a larger X127.5 main jet and 100Z or 120Z air correction jet are needed. Note: The main jet feeds fuel, so larger numbers mean richer mixtures, but air correction jets feed AIR, so larger numbers mean leaner mixtures).
The pilot jet is sized correctly if the fuel screw setting falls between 2.5-3 turns out. The pilot jet is sized correctly if the air screw setting falls between 1-2 turns out, with 1.5 being the sweet spot.
Here is a table made from the formula: So lets say you take your bike and put on a new pipe, airbox, and such and get it jetted well in Denver on a 60 degree day (CF=.963). Lets say the main jet that runs best is a 180. Your new STP main jet is a 180/.963 = 187.
How big of a pilot jet do I need to fix lean back?
In most cases screw adjustments won’t correct the lean back firing, installing a one size larger pilot jet will do the trick for higher elevations (Colorado). Carburetor diameter (12mm) x 5 = 60 (or number it calculates) x 0.9 = sea level jet size
What are the specs for a jetting carburetor?
I am going to list stock, as received, and the final jetting specs I ended up with. I have a detailed post here on How-To jet a 4 stroke carburetor.