Page 19 - Arrow Shark X-60 Owner Manual

Needle Setting

The X-60 comes with a Arrow Shark M-39X Pro-Mod
carburetor as mentioned above, and the carb has been
pre-set at the factory. However, it may require little
adjustment to compensate for different ambient
conditions such as varying temperature, humidity,
altitude, etc. The carb has three adjustments - the low
and high speed needles and the idle screw.

A: The Low-Speed Needle: The low speed needle
of the M-39x carburetor is hidden in the center of
the carburetor barrel. You need to use a small
precision flat blade screwdriver to adjust it. When
adjusting the Low-Speed Needle, apply
Loctite#222 on the needle thread in order to hold
the needle in position during operation.

The Low-Speed Needle is set at 7 turns out from
fully closed (or fully screwed in).

B: High-Speed Needle: The High-Speed Needle is set approximately
2 turns out from fully closed.

C: Idle Screw: Set this at the lowest RPM where the engine idles reliable without
stopping. Screwing the idle screw in will make your engine rev faster.

Setting Your Throttle Servo

You will need to adjust the radio settings for your throttle servo. This needs to be set so that the engine idles
smoothly when your radio transmitter trigger (or other throttle control if not a wheel/trigger transmitter) is at
its neutral position. You may need to adjust the throttle pushrod linkage and/or use your throttle trim to
adjust the idle speed up or down to get a reliable idle. When your trigger is pulled fully open for high speed,
the servo movement should have the engine’s throttle barrel fully open. You may need to adjust your
pushrod linkage and/or the servo’s travel so that the throttle barrel is fully open with the trigger pulled all the
way, but the servo should not stall by trying to force the barrel further than it will go. Finally, the servo
should be adjusted so that it fully closes the barrel and stops the engine when you push the trigger (or apply
the “brake” in RC car terms).
Your radio should also be equipped with a “Fail Safe” system which closes the throttle in the event of radio
failure or loss of signal. If this is not an integral facility within your radio, you will need to fit a separate Fail
Safe – these are readily available from good hobby stores. Follow the radio or Fail Safe instructions and set
it so that the M-39X barrel is fully closed when your transmitter is turned off.

M-39X Adjustment Tips

When adjusting the needles from their standard settings, move them only 1/8 of a turn a time. Check the
results then adjust further as needed. Never attempt to tune the high-speed needle by running the engine at
full throttle out of the water! This is very dangerous and damages the engine. The following tips may assist
in setting your M-39X Carburetor for optimum engine performance.

19