UMS 7-90 cc User Manual page 7

Installing the Electronic Ignition
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 ring order and the engine will not
run correctly.
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.
Engine Cooling Requirements
It is very important to consider adequate cooling inside the airplane cowl. Engines require
a cooling airow 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 owing through the cowl and
the cylinder head ns. Achieving the proper ratio typically requires cowl and/or engine
bafes to reduce the open intake area.
1. Ensure there is adequate cooling air moving through the cylinder head cooling ns.
The intake air tends to move through the path of least resistance (between the cylinders)
instead of through the cylinder cooling ns.
2. If necessary, add bafes to the engine to prevent air from moving between the cylinders.
Engine bafes force cool air through the cooling ns and greatly reduce the intake area
in the front of the cowl.
3. Add cooling bafes 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 bafe. 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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