How do I know if I need to Rejet my carb?
A clean spark plug means you can skip the rejet. A black, sooty-looking spark plug means you’re running rich with too much fuel in your mix. If you see white residue, that means you’re running lean with too much air. In both cases, you need a rejet.
Do carb jets affect idle?
As far as jetting goes, the jet size will not affect idle, as the jets don’t come into play until the carb transitions to the primary circuit, unless the throttle blades are open far enough to expose the transfer slot. If this is the case, the throttle blades need to be closed enough to cover up the transfer slot.
How do I know if my carburetor is rich or lean?
Q: How Do You Tell if a Carburetor Is Rich or Lean? A: One way to tell for sure is by “reading” the spark plugs. If the plug tip is white, the mixture is lean. If it’s brown or black, it’s rich.
How do you tell if a carburetor is rich or lean?
Typical symptoms of a rich mixture are:
- Poor fuel economy.
- Sluggish acceleration.
- Choke not needed from cold starts.
- Sooty or black spark plugs.
- Sooty or black muffler end pipes.
- Strong smell of gasoline when the machine is at idle.
- Uneven running (will often slow from regular idle rpms and then stop)
Are carb jets universal?
Yeah, most Keihin jets are interchangeable and most Mikuni jets are interchangeable (though the two brands are not interchangeable with eachother). Any motorcycle dealer should be able to get jets for your bike even if they do not sell the brand of bike you have.
What do Jets do in a carburetor?
The main jet provides the fuel at 80 percent to wide-open throttle. The fuel flows up and out through the needle jet into the throat of the carburetor. When changes in air density are significant the main jet will need to be swapped.
How do I know if my jet is too small?
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.
What is needle jet?
The needle jet (AKA main) is the calibrated hole that the needle fits into. If you roll the needle on a plate of glass you will see any imperfections that could effect performance. The needle should have grooves in the top for positioning it in the slide. Move the clip up, the needle goes down and leans the mixture.
Does Jet needle affect idle?
The needle position has no affect on idle, it basically affects mixture around the 1/2 throttle range. If you need to change the WOT mixture you need to change the main jet, then change the needle to suit half throttle needs.
Does main jet effect idle?
The main jet does not effect the jetting for starting and idling. It plays no part on low RPM or mid RPM jetting either.
What happens if main jet is too big?
For example, using too large of a main jet will cause more fuel to enter the combustion chamber than it can efficiently burn. This will result in a “sputter” at full throttle. It could best be described as a rapid misfire.