UMS 5-55 cc User Manual page 7

Installing the Electronic Ignition
An ignition cables are labeled for each cylinder by the numbering system. please make sure
you connect the cables to the correct spark plugs / cylinders.
The electronic ignition requires a 6—7.4V 2500mAh battery. For the best performance,
we recommend a 7.4V 2S Li-Po battery (minimum 2500mAh) and a suitable switch (JRPA001).
A voltage regulator is not required for use with a 7.4V 2S Li-Po battery.
An electronic ignition is included with your engine. The spark plug wires are labeled for each
cylinder—ensure the spark plug wires are connected to the correct cylinders. Connecting the
spark plug wires to the incorrect cylinders will change the firing order and the engine will not
run correctly.
Engine Cooling Requirements
It is very important to consider adequate cooling inside the airplane cowl. Engines require
a cooling airflow exhaust:intake ratio of 3:1 to 5:1. A large open cowl may lead you to believe
there is adequate cooling; however, you must make sure air is flowing through the cowl and
the cylinder head fins. Achieving the proper ratio typically requires cowl and/or engine
baffles to reduce the open intake area.
1. Ensure there is adequate cooling air moving through the cylinder head cooling fins.
The intake air tends to move through the path of least resistance (between the cylinders)
instead of through the cylinder cooling fins.
2. If necessary, add baffles to the engine to prevent air from moving between the cylinders.
Engine baffles force cool air through the cooling fins and greatly reduce the intake area
in the front of the cowl.
3. Add cooling baffles to the engine cowl between the top of the cylinder heads and the inside
of the cowl.
4. Do not cover the engine exhaust tube with the baffle. The exhaust tube requires direct
air cooling to prevent damage to the exhaust valve.
NOTICE: Always observe proper polarity when
connecting the ignition battery to the ignition
unit. The ignition unit does not include reverse
polarity protection. Ignition unit damage
caused by reverse polarity is not covered
under warranty.
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