|What is a jet? Is Piped and jetted
like Bored and Stroked?
A engine needs to have Air and
Fuel in the correct mix to run at top power.
The pilot jet is a small
jet for idle speed. The pilot jet air mix is adjusted with the air
Most air screws are set about 1 and 1/2 turns out. The slide needle is
a long needle with a
circlip to position it in the throttle slide. The slide needle controls
fuel mixture at 1/4 to 3/4 throttle. It is adjusted by raising or
lowering the needle to control the amount of fuel that is allowed
the main jet. The main jet is for 3/4 to wide open throttle.
on a moped that control the air fuel mixture are the carburetor and air
box. Inside the carburetor there are holes made to an exact size that
fuel to pass through and mix with the air. These orifices are called
Here are some things that affect jet
-Changing air cleaner,
air box will affect how much air gets to the carburetor.
-Cleaning or oiling the air filter will
affect how much air can get through it.
How do I tell if I am running Rich or Lean?
When rich, (too
much fuel) the engine sputters, acts like it is cold, won't warm
up, does not clean out, chugs, spark plug gets black, plug fouls, won't
rev up.\ When Lean, (Not enough
fuel) Dies out, Wheezes, runs out of gas, Seizes, gets hot,
spark plug is white, spark plug has little melted gobs on
warms up fast, you can start engine cold and rev it right up.
Why did my piston seize?
On a two cycle engine, the fuel cools the piston. If you do not
enough fuel through to keep the piston cool, it will get too large for
the hole in the cylinder and stick. If you
add more oil to the fuel, that means even less fuel cools the piston
it will seize even more. If your
piston sticks, that means you are running to lean.
If your connecting rod sticks,
THAT means you need more oil.
What can I do to experiment?
To make it lean open up the
air box a bit make sure the intake boots are not
shrinking down clean out the air filter remove the air box. To
make it rich: Close
off the intake holes in the air cleaner box. Hope