Sportwerks Mayhem, Руководство по сборке и эксплуатации, Страница: 11 / 40

Page 11
Adjusting the Carburetor
Tuning your Engine
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 “Fine
Tuning Your Engine”)
Fine-Tuning Your Engine
As you gain experience, you’ll be able to tune
your engine based on the engine’s sound and
feel during acceleration and at full throttle. Until
you’ve developed this skill, we recommend the
following method of engine tuning.
Start your engine and drive your buggy
aggressively for about two minutes.
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 slowly, in about 5–10 seconds.
If the water does not evaporate, the needle
setting is too rich. Lean the high-speed needle
1/8 of a turn and run the engine again, adjusting
the needle setting to get the desired evaporation
rate of 5–10 seconds. 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 engine’s proper
operating temperature, reduce the engine throttle
to idle for about 15 seconds. Now pinch the fuel
line with your fingers
close to the carb fuel inlet nipple while carefully
listening to the engine RPM. If the engine dies
immediately without an increase in RPM, the low-
speed needle is set too lean.
If the RPM ’s increase dramatically and then the
engine dies, the setting is too rich.
The ideal setting results in the RPM ’s increasing
a slight amount (about 200 RPM’s) after pinching
the fuel line before dying.
Setting the Idle RPM
The last setting to be made is the idle RPM.
Turning the idle stop screw clockwise increases
the idle speed; whereas turning the screw
counterclockwise will make the engine idle at a
lower RPM. Ideally, the engine should idle just
fast enough to give a reliable idle but not engage
the clutch and, of course, never flame out.