User Manual

Do not skip this process of breaking in a new
engine! Should you choose not to follow these
procedures, you risk damaging your engine
during the first tank of fuel.
Your patience during these procedures will be rewarded
by an engine that performs reliably and to its maximum
power potential. First-run attempts can be more
frustrating than with other (less powerful) sport engines,
so take your time—it will be worth the wait. Glow plug
failure is a common occurrence when breaking in a
new engine. To test your plug, let the engine idle at a
properly adjusted low-speed needle setting with the glow
igniter attached. Then, remove the igniter. If you hear no
appreciable change in engine rpm, the plug is still good.
If the engine loads up and the rpm’s decrease, it’s time to
replace the glow plug.
Setting the Needle Valves
When tuning the needle valves for maximum
performance, adjust them in small increments,
1⁄16 turn at a time.
An engine should not be run too lean; doing so severely
shortens the life of the engine. When an engine is set too
lean, it will run very strong at first but will soon begin to
sag and hesitate or stall when accelerating.
The best way to tune an engine is by using an infrared
temperature gauge, but you can also use water to check
the head temperature (refer to “Tuning the High-Speed
Needle”).
Carburetor Restrictors
The Dynamite 21 engine features a slide-valve carburetor
and includes three inserts of various diameters. These
carburetor inserts are used to alter the power curve of the
engine. The three diameters included have the following
effect:
7.5mm
Develops good mid-range power; easier to control than
the 9mm insert; best for medium traction, average-sized
tracks/areas.
8mm
Increased power for high traction, medium-to large-
size tracks; slight decrease in fuel mileage over the
7.5mm insert.
8.5mm
Offers explosive, sometimes difficult-to-control
acceleration; uses the most fuel; used only for high
traction, large track/open areas; for expert drivers only.
Engine Maintenance
Periodic maintenance must be performed in order
to keep your engine in proper operating condition. After
each day of running, it’s critical to use high quality after-
run oil to protect the internals of the engine and help
prevent corrosion. The methanol used in the fuel attracts
moisture that can cause corrosion (particularly in the ball
bearings). Follow these steps after running your engine:
1) Empty all fuel from the tank and fuel lines.
2) Remove the glow plug and air filter and add 5 to 6
drops of a quality after-run oil into the carburetor
and cylinder head openings. Turn the engine over
a few times to distribute the oil throughout the
engine.
3) Clean and inspect the engine, air cleaner and
fuel system.
Troubleshooting Guide
Problem
Engine won’t start
Engine starts, then dies
Engine starts and runs
for 1⁄2 tank, then quits
Tuning the High-Speed Needle
To obtain the correct high-speed needle setting, start the
engine and drive your vehicle around for a minute or two,
applying full throttle frequently. Place a drop of water on
the cylinder head. If the water sizzles away (evaporates
immediately), the needle setting is too lean. A correct
needle setting will result in the water evaporating after
3-5 seconds. If the water does not evaporate, chances are
good that the needle setting is too rich. Lean the needle
1/16 of a turn and run the engine again, adjusting the
needle setting to get the desired evaporation time.
Check the temperature each time you change
the needle mixture. Do not let the engine
overheat, as this will damage the engine.
Tuning the Low-Speed Needle
The low-speed needle (also referred to as the idle mixture
or idle needle) should be set after you’re satisfied with
the high-speed needle setting. After achieving the proper
operating temperature, reduce the engine throttle to idle
and pinch the fuel line with your fingers close to the
carb fuel inlet nipple. If the engine dies immediately, the
low-speed needle is set too lean. If the rpm’s increase
dramatically, the setting is too rich. The ideal setting
results in the rpm’s increasing just a slight amount after
pinching the fuel line.
Idle Stop Adjustment
The last setting to be made is the idle stop screw. Turning
this screw clockwise increases the idle speed, whereas
turning the screw counterclockwise will make the engine
idle at a lower speed. Ideally, the engine should idle just
fast enough to be reliable in acceleration and transition
from idle to full speed. Avoid an idle speed that is too fast,
as it will cause damage to your clutch.
Possible Cause/Solution
• Clogged fuel line
• Bad or improper glow
plug
• Glow igniter not
charged
• Engine flooded
• Pressure line blocked or
disconnected
• Bad glow plug
• High-speed needle too
lean
• Hole or tear in fuel line
• Bad glow plug or idle
speed set too low
• Overheated engine
(too lean)
• Improper needle
settings