Low-Speed Needle; Engine Tuning - Team Losi Speed NT Manual

Engine Break-In and Adjustments
The new Losi 3.4 engine in your Speed-NT has been machined
to tight tolerances and does not need an extended break-in. It
is always a good idea to take it easy for the first few tanks of fuel
to let all the gears and moving parts seat into one another. You
will notice after the first hour of operation that the engine will
pick up power. It is highly advised that you use Nitrotane 20%
Sport fuel as the carburetor is factory set for this fuel and other
fuels may require immediate needle valve adjustments. NEVER
use model airplane fuel as it may cause damage to the engine
and void any warranty. If you change fuels or run in dramatically
different environments (hot/cold, high/low elevation, etc) you
will probably have to adjust at least the high-speed needle to
prevent overheating and maintain proper performance.
Understanding "Rich" and "Lean" Fuel Mixture
Adjusting the carburetor is one of the most critical facets of
running a nitro powered RC vehicle. The fuel mixture is referred
to as being "rich" when there is too much fuel and "lean" when
there is not enough fuel for the amount of air entering the
engine. The amount of fuel entering the engine is adjusted with
high- and low-speed threaded needle valves. The low-speed
needle is located in the front of the moving slide. The high-
speed needle sticks straight up at the back of the carburetor.
Both feature a slotted head that is used as a reference and
receptacle for a flat blade screwdriver for adjustments. The
mixture is made richer by turning the needle counterclockwise
and leaner by turning clockwise. An overly "rich" mixture will
yield sluggish acceleration and performance with thick smoke
from the exhaust. A "lean" mixture can cause the engine to
hesitate before accelerating or, in some cases, to lose power
momentarily after the initial acceleration. A lean mixture also
makes the engine run hotter than desired and does not provide
enough lubrication for the internal engine components,
causing premature wear and damage. It is always advisable
run the engine slightly rich
to
overheating and possible damage.
Base Start-up Settings from the Factory
High-Speed Needle—2 / turns out from bottom
3
4
Low-Speed Needle—2 / turns out from bottom
3
4
Slower
never lean
and to avoid
Faster

Engine Tuning

After the engine is broken in, you can tune it for optimum
performance. When tuning, it is critical that you be cautious of
overheating as severe damage and premature wear can occur.
You want to make all carburetor adjustments in "one hour"
increments.
Rich
3
1
1= Idle Stop Screw

2=Low-Speed Needle

3=High-Speed Needle
Rich
Low-Speed
Needle
9
Lean
Lean
Carb Adjustments:
Make all carburetor
adjustments in one-hour
increments.
Imagine the slot in the
needle is the hour hand on
a clock. Adjust it as though
you were moving the hour
hand from one hour to the
next or previous one.
2