Which jet is responsible for idle?
pilot jet
The pilot jet along with the mixture screw is responsible for how your bike idles. It also provides the fuel for about the first 15 to 20 percent throttle.
When should I increase my main 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.
Is the needle jet in play at idle?
As Fin points out, the slow jet is in play at idle to about 1/4 throttle and sizing that jet properly (45 may be right) would be worth checking. JMHO but the A/F screw should not be used to control fuel passing through the needle jet; that is the job of the needle and needle jet.
Where is the needle jet in a carburetor?
The needle jet—or nozzle as it’s sometimes called—is located in between the main jet and the carburetors venturi. Fuel comes through the main jet and into the needle jet. So the main jet does affect the needle, especially as the throttle opening increases. The needle is attached to the slide and slides up and down within the needle jet.
Why is fuel not passing through the main jet?
First, I would be skeptical that fuel is passing through the main jet at idle. The needle jet/needle is the control over fuel passing through the main jet; if the needle is seated properly and the needle jet installed properly, fuel cannot pass through the main jet.
Why does fuel foul the plug at idle?
The diameter of the needle does allow some fuel into the intake stream via the needle jet at idle and up to about 1/4 throttle and even if he needle has been raised, the amount of fuel passing the needle jet is marginal will never be enough to foul plugs. I still don’t believe the plug fouling is caused by fuel passing through the needle jet.
As Fin points out, the slow jet is in play at idle to about 1/4 throttle and sizing that jet properly (45 may be right) would be worth checking. JMHO but the A/F screw should not be used to control fuel passing through the needle jet; that is the job of the needle and needle jet.
Do you need a jetting chart for a two stroke carburetor?
A standard jetting chart for two and four-stroke carburetors provides guidance on the attributes of the pilot screw, slow jet, needle clip position, needle type, and main jet. Many OEM owner’s or service manuals will include jetting charts suggesting what changes to make based on altitude and temperature.
What to do when CV carb pulls fuel through main jet at idle?
The fuel is being pulled through the main jet at idle, fouling the plugs. Took the carb apart, cleaned all the passages with carb cleaner and compressed air, set the float according to the manual, replaced the o rings, all the things you’re supposed to do.
First, I would be skeptical that fuel is passing through the main jet at idle. The needle jet/needle is the control over fuel passing through the main jet; if the needle is seated properly and the needle jet installed properly, fuel cannot pass through the main jet.