Demon Fuel Systems 1905 - Manual (Page 10)

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3. The 14” Demon air cleaner (Part # 786004) is designed to clear the choke plate linkage on all Demon carburetors. If
you use another brand of air cleaner / air cleaner gasket or air cleaner spacer, it is necessary to make sure that the
full range of motion of the choke shaft and butterfly are realized. Failure to do so could result in the choke not
operating properly. This may cause an overly rich condition and/or a high idle condition, which could make the vehicle
hard to control and stop.
CAUTION: As with any modification, inspection of the part after completion is a must. Before use, check the
linkage for freeness of operation. Your safety depends on it.
PERFORMANCE TUNING AND ADJUSTMENT
Once you have completed the initial installation, and preliminary adjustments, you are now ready to test the vehicle and
evaluate any other possible tuning adjustments. Information on changing the configuration or fuel metering of your Demon
is also included in this section.
Secondary Air Valve Tuning
The secondary air valve door is designed to dampen the transition from primary to secondary operation. Controlled by a
torsion spring, the secondary air valve door is tunable to permit seamless primary to secondary throttle response
regardless of the throttle rate opening.
Figure 14
The factory setting for the secondary air valve door is the most common setting which is 1 ½ full turns counter-clockwise
after the air valve door is completely closed. If tuning is desired, using a flat blade screwdriver engage the adjusting screw
then loosen the lock nut (If the locknut is loosened before engaging the adjustment screw, the spring tension will be
released - Fig. 14), turn the adjusting screw counter-clockwise to increase spring tension on the door and delay opening.
Turn the screw clockwise to decrease tension and allow the door to open sooner. It is not recommended to go beyond
one turn more than the factory setting (torque to 50-60 in./lbs.). Tighten the lock nut to hold the adjusted position. As an
example, you experience a hesitation or backfire when the secondaries open. This means the secondary air door is
opening to quickly, so it is necessary to adjust the door tighter (counterclockwise) until the hesitation disappears. It is
recommended to only adjust the door ¼ turn at a time an retest for the condition.
CAUTION: Adjusting the secondary air valve door too loose can cause the door to open a small amount at idle
or low RPM cruising, resulting in an undesirably rich condition.
Accelerator Pump Tuning and Adjustment
When the throttle plates are in the closed (curb idle) position, there should be no play in the accelerator pump connecting
rod. The pump lever should begin compressing the pump stem as soon as the linkage begins to move. Incorrect
adjustment of the pump arm linkage will delay the fuel discharge, and the result is usually a stumble or hesitation as the
butterfly begins to open.