How do I know if my pilot jet is too lean?
If the bike surges or hunts, the pilot jet is probably too small (lean). Other indications that the pilot circuit is lean are popping or spitting through the carburetor when the throttle is opened and popping or backfiring through the exhaust when the throttle is shut.
How do I know if my pilot jet is too big?
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.
When should you increase pilot jet size?
A general rule is to increase the main jet as long as each jet causes the engine to run as well as or better than the smaller jet in it before. When there is no longer any additional performance gain from the larger jets the jet size is too big – go back down one size.
How do you tell if a carburetor is rich or lean?
This method involves looking at the base of the spark plug insulator (white part of the plug) for a slight coloring on the insulator just above where the insulator comes through the steel case. If the mixture is too lean, it will leave no color, while a rich mixture will cause the fuel ring to become more prominent.
What does a smaller pilot jet do?
The smaller the holes in the jets, the less fuel in the air and, as a result, less explosion and less power to run your engine. By replacing your current jets with ones that have different sized holes you can add either more fuel or air to perfect your motorcycle’s fuel-air ratio.
How many jet sizes go down?
When the operating altitude of the engine will be 2000 feet higher than your normal altitude, you’ll need to insert a jet one or two sizes smaller than the size currently installed in the carb, which reduces the amount of fuel entering the engine to match the reduced level of oxygen in the air.
Is backfiring lean or rich?
Lean Air/Fuel Mixture Not only can a rich air/fuel ratio cause a backfire, a mixture that doesn’t have enough gasoline can cause a backfire, too. When a lean mixture combusts, it burns more slowly, meaning there will still be some air and fuel that isn’t used up when the exhaust valves open — leading to a backfire.
How do I know if my carburetor needs adjusting?
The engine should rev smoothly and quickly as soon as you apply throttle. If the vehicle is displaying any sort of sluggish performance or misfires when you apply the throttle, then more adjustments are required.
How do I know what size jet I need?
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 choose a jet size?
A larger jet number means a bigger hole and more fuel. A smaller jet number has smaller holes and should be used if your engine needs to run more lean. Whether your machine is running too lean or too rich is a good starting point for choosing your jets, but using a jet calculator minimizes trial and error later.
How do I change the jet on my carburetor?
The jets are located in the bottom of the carb. Remove the 4 screws which attach the fuel bowl to the carburetor. Once the 4 screws are removed the main jet and slow (or pilot) jet can be removed. 3) Pilot jet (Slow jet): If unable to obtain a smooth idle with pilot screw, increase the pilot/slow jet until a smooth idle can be obtained.
How to tell if the pilot jets are too big?
The fuel screws should be responsive. They should both be turned out the same amount. If you can close them and engine still runs, the pilot jets are too big. An IR temp gun can be handy for aiming at pipes to read temps and help understand what is going on.
What is the difference between the original and replacement Slow Jets?
There are three jets, Slow Jet, Primary Main Jet and Secondary main jet. The replacement slow jets seem to be different than the original. The little holes on the side are smaller on the replacement, and the center hole, as small as it is, seems smaller on the replacements too.
Where is the pilot air screw located on a carburetor?
Where is the pilot air/fuel screw located? Let’s define the carburetor butterfly or slide the dividing line between the air box side, and the engine side. A pilot air screw will be located on the air box side, while a fuel screw will be located on the engine side. This is true for most carburetors.