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 2-3/4 turns out from the fully
closed position of the carb. Once the engine is broken-in,
the high-speed needle would typically run 2 to 2-1/2 turns out
from closed, depending on the weather, humidity and altitude
above sea level. To richen the mixture turn the needle
counterclockwise. To lean it turn the needle clockwise.
The engine is factory set. Adjustments may need to be
made to obtain optimum performance.
The “low-speed” needle is located on the side of the carburetor.
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
speed, 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.
On the front of the carburetor, there is a black screw. This is
called the idle stop screw. This increases or decreases the
idle RPM without changing the fuel to air mixture.The barrel
should be approximately 1.5mm (between 1/32" and 1/16")
from fully closed.
To insure long life and good performance from your Velocity
.17 engine, you MUST break-in the engine. The break-in
period is critical for long life of the internal parts of the
engine.This should be done over the first 4 or 5 tanks of fuel.
SOME THINGS TO REMEMBER DURING BREAK-IN:
❏ 1. Run with the body off.This will keep the engine cooler.
❏ 2. Keep the air cleaner on at ALL times
❏ 3. Run on a smooth, hard surface. An empty parking lot
is perfect.
❏ 4. Use the same fuel that you will use for normal running.
❏ 5. Resist the urge to accelerate and decelerate the
truck quickly.
❏ 6. Break-in puts stress on the glow plug and you can burn
it out during break-in. Make sure you have an extra plug or
two on hand.
❏ 7. Do NOT overheat the engine.You can check the head
temperature by using one of the temperature gauges that
are available or by putting a drop of water on the top of the
cylinder head. If the water boils away immediately, shut off
the engine and allow it to cool. If it takes more than 5
seconds to boil away, the engine is at proper running
temperature for break-in.
Before running the engine, read the manual and watch
the engine video that came with this kit.
ENGINE BREAK-IN
THROTTLE STOP SCREW
LOW-SPEED NEEDLE
HIGH-SPEED NEEDLE
5
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