Sportwerks Mayhem ST, Руководство по сборке и эксплуатации, Страница: 11 / 36

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 truck 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.