Losi LOSB0013 User Manual

Required Equipment

You will need the following items to operate your new Mega Baja.
8 AA Alkaline batteries for the transmitter
Losi® Nitrotane™ 20% Sport Fuel. (LOSF0020 or LOSF0120) This is the only fuel that supports the engine warranty.
Fuel bottle (LOSB5201)
Optional: Rechargeable Glow Ignitor (LOSB5221)

Tools You Will Find Handy

In addition to the tools included with the Mega Baja, you will find the following both useful and in some cases necessary.
Small flat blade and Phillips screwdrivers
Needle-nose pliers
Quality .050", 1/16", 5/64", 3/32", 1.5mm and 2.5mm hex (Allen) drivers

Understanding "Rich" and "Lean" Fuel Mixture

Adjusting the carburetor is one of the most critical facets of running a nitro powered R/C 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 to run the engine slightly rich
and never lean to avoid overheating and possible damage.

Engine Break-In and Adjustments

Breaking in your new engine is critical for proper performance. Failure to follow the break-in procedures can cause
damage and shortened engine life. During break-in and when running, always use Losi Nitrotane 20% Sport Fuel.
Although the carburetor is preadjusted at the factory, you must be familiar with the following adjustments and
break-in procedure. If you change fuel 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. Never, under any circumstances allow the engine to rev freely with the wheels off the ground.

Break-In Procedure

1.) The first three tanks of fuel should be run with the high and low speed needles noticeably "rich" (see explanation
below). There should be a slight sluggishness and thick smoke when accelerating with the smoke decreasing as the model
gains speed. At speed, there should still be a noticeable trail of smoke from the exhaust pipe. Run the Mega Baja on a flat
surface in an oval pattern. Ease into the throttle as you accelerate on the straight sections, easing off as you approach
turns—letting the model roll through the turn before easing back on the throttle. This will also allow you to get a feel
for the steering response and handling characteristics of the model.

2.) You can also break in the engine by placing the model against a wall or fixed object and allow the engine to idle
through two full tanks of fuel. You may have to lean the low speed mixture (slightly) as noted below.

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Base Start-up Settings from the Factory

High-Speed Needle—31/2 turns out from bottom
Low-Speed Needle—21/2 turns out from bottom

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.

1 Hour

2 Hour

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.

Low Speed Adjustment

The low speed adjustment affects the idle and slightly off idle performance.
The optimum setting allows the motor to idle for at least 8−10 seconds. The model
should then accelerate with a slight amount of sluggishness and a noticeable
amount of smoke. The simplest way to check this is to make sure the engine has
been warmed up and let the engine idle for 8−10 seconds. If the low speed mix­ture is so far off that the engine won't stay running this long, turn the idle stop
screw clockwise, increasing the idle speed. With the engine at idle, pinch and hold
the fuel line near the carburetor, cutting off the flow of fuel, and listen closely to
the engine rpm (speed). If the low speed needle is set correctly, the engine speed will increase only slightly and then die.
If the engine increases several hundred rpm before stopping, the low speed needle is too rich. Lean the mixture by turning
the needle clockwise one hour and trying again. If the engine speed does not increase but simply dies, the needle is too
lean and needs to be richened up by turning the needle counterclockwise one hour before trying again. After you have
optimized the low speed setting, the engine will probably be idling faster. You will have to adjust the idle stop screw
counterclockwise to slow down the engine idle speed. The engine should accelerate at a constant pace without
hesitating.

High-Speed Needle

As you turn this clockwise (leaner),
less fuel enters the engine.
Turning it counterclockwise
(richer) allows more fuel to enter
the engine.

Idle Speed Screw

As you turn this clockwise, it
increases the carburetor opening
at idle and increases idle speed.
Turning it counterclockwise
decreases the opening and idle
speed.

Low-Speed Needle

As you turn this clockwise (leaner),
less fuel enters the engine.
Turning it counterclockwise
(richer) allows more fuel to enter
the engine.

Richer

Leaner

Idle Speed

Screw

Faster

Slower

High-Speed

Needle

Carb Opening

Leaner

Richer

Low-Speed

Needle

Hi-Speed Adjustment

After initial acceleration, the engine should pull at a steady rate while maintaining a two-stroke whine and a noticeable
trail of smoke. If the engine labors and is sluggish with heavy smoke, the mixture is too rich and needs to be leaned
by turning the high-speed needle clockwise in one-hour increments until it runs smoothly. If the engine isn't smoking or
starts to die after acceleration, it is too lean and you must richen the mixture by turning the needle counterclockwise. Don't
be confused by the sound of the engine and the actual performance. A leaner mixture will produce an exhaust note with a
higher pitch but this does not necessarily mean improved performance, as the engine is on the verge of overheating and
may incur possible damage. Ideally you want to run the engine so that it is on the slightly rich side of optimum.
This will give you the best combination of speed and engine life. CAUTION: The engine is too lean and overheating if it
accelerates rapidly with a high-pitched scream then seems to labor, stops smoking, or loses speed. This can be caused by the
terrain, atmospheric conditions, or drastic altitude changes. To avoid permanent engine damage, immediately richen the
mixture by turning the high-speed needle counterclockwise at least "two hours" and be prepared for further adjustments
before running any more.

About Glow Plugs

The glow plug is like the ignition system in your automobile. The coiled element in the
center of the plug glows red hot when connected to a 1.5-volt battery (located in the igniter).
This is what ignites the fuel/air mixture when compressed in the cylinder. After the engine fires,
the heat generated by the burning fuel keeps the element hot. Common reasons for the engine
not starting are the 1.5-volt battery being weak or dead, the glow plug being wet with fuel, or the
element burned out. Use a spare glow plug to check the igniter. If the igniter makes the element
glow, remove the plug from the engine to check it in the same manner. A wet glow plug means there is excess fuel in
the engine. To eliminate this, put a rag over the head and turn the engine over a few seconds with your "Spin-Start."
Reinstall the glow plug, making sure you have the brass gasket on it. The engine should now start.

Testing the Temperature

The ideal operating temperature for the engine will vary with the air temperature but in general it should be in the
200°F to 230°F (93.3°C to 110°C) range. A simple way to check the engine temperature is to put a few drops of water
on the top of the head/heat sink. It should take 3−5 seconds for the water to evaporate. If it boils away quickly the
engine is overheating and the high-speed needle needs to be richened (turned counterclockwise) at least "two hours."
If you plan on racing or prolonged high-speed running, there are several inexpensive handheld digital temperature
gauges available, like the LOSA99171, you may want to invest in.

About the Radio

The JR radio installed in the Mega Baja is a professional level system with more than the
usual features you may find useful. Be sure to read through the included radio manual
for complete instructions. The following is a simple guide refers to items that are
commonly used and/or needed to run your model.

1. Power Switch - Turns your transmitter ON and OFF

2. Steering Wheel - Controls the steering of your model

3. Steering Trim Tab - Allows you to fine-tune the neutral
position of the steering

4. Throttle Trigger - Pull back for throttle and push forward for brakes

5. Throttle Trim Tab - Allows you to set the idle/brake of the model

6. Transmitter Dislay - Digital readout shows battery voltage, frequency,
feature functions/settings

7. Transmitter Antenna - Transmits signal to the receiver in the model

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DYN2500 Shown

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