The High-Speed Needle
The “high-speed” needle is sticking up from the side of
the carb. It is located in the brass housing, just above
the fuel inlet. It controls the fuel-to-air mixture of the
carb. The needle is pre-set for break-in from the
factory at 2-1/2 turns out from the fully closed position
of the carb. Once the engine is broken-in, the high-
speed needle would typically run from 2 to 2-1/2 turns
out from closed, depending on the weather, humidity
and altitude above sea level. To richen turn the needle
counterclockwise, to lean turn the needle clockwise.
The Low-Speed Needle
The “low-speed” needle is the screw in the carb body,
opposite the throttle arm. It controls the fuel to air
mixture at low throttle settings. There is a simple way of
adjusting the low-speed needle correctly called the
“pinch test.” With the engine at idle, pinch the fuel line
and listen to how the engine speeds up or slows down.
If the engine increases its speed for about 2 or 3
seconds and then loses RPM, the needle is set
correctly. If the engine loses RPM quickly, it is set too
lean and the low-speed needle needs to be opened
(counterclockwise)
to richen the mixture. Pinch again
to check the mixture. If the engine takes longer than 4
seconds to slow down, lean
(clockwise)
the low-speed
needle and then pinch again to check the mixture.
The Throttle Stop Screw
On the front of the carburetor, there is a black screw.
This is called the throttle stop screw. This increases or
decreases the idle RPM without changing the fuel-to
air-mixture. You should see an openning of
approximately 1.5mm (between 1/32” and 1/16”)
between the carb body and the carb barrel when the
throttle is pushed closed.
Before running the engine, read everything in this
manual concerning engines and watch the engine
video that came with this kit.
There are several simple steps to starting the engine:
1. Install a glow plug if one is not in your engine. This
threads into the top of the cylinder head.
2. Fill the tank almost to the top. Leave a little air at the
top of the tank.
3. Prime the engine by turning the flywheel on the
engine. Watch the fuel go through the line and
when it gets to the carburetor, turn the flywheel one
more full revolution.
4. Open the high speed needle valve exactly 2-1/2
turns out
(counterclockwise)
from fully closed. Be
careful not to overtighten the high speed needle.
When you feel some resistance, stop turning the
needle.
The high-speed needle is sticking up
from the carburetor inside the brass housing.
All of the carburetor settings are adjusted with a flat
bladed screwdriver. If you have previously run the
touring car, keep the same needle valve setting that
you used on your last run.
5. Start the engine by pulling the recoil - Use short,
quick pulls.
DO NOT
pull the recoil starter’s string to
the end. You only need 10 to 12 inches of pull to
start the engine.
If the engine does not start after several pulls,
sometimes it is helpful to start the engine at around
half throttle. Have a friend pull back on the throttle
some while you start the engine. This
may
be an
indicator that the low speed needle setting needs to be
adjusted. When the engine starts, immediately return
the throttle to idle. If this is not done the engine can
RUNNING THE ENGINE
1/32" TO 1/16" GAP
CARBURETOR SETTINGS
11
