How to time the ignition on a Rotax 447 aircraft engine.
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Timing the Rotax Ducati CDI Aircraft Engines
Several years ago Rotax changed the ignition
system they used on their aircraft engines from points and
condensers to capacitor discharge ignition or CDI for short. On
the first engines the TRIGGERS were bolted into
place, allowing for NO adjustment in the timing of the engine.
Current mod els
have slotted ends on the triggers which means that the engine
timing can be checked and adjusted if necessary.
To properly set the triggers a dial indicator with extensions and
rollers is required - Rotax has a kit which while expensive does
the job - part # 414-1047.
To set the TRIGGER in the correct location
requires the insertion dial indicator into the magneto spark plug
hole - the dial indicator MUST has a roller contact or roller ball
on the end of the extension arm, due to the angular spark plug
hole.
You only need to install the dial indicator into the magneto hole,
since it is used to set both sides of the engine. Once the
indicator reads correctly for the engine you are working on you
simply move the TRIGGERS so that they are as
indicated in the above diagram.
Once set in the proper location make sure that the air gap is also
correctly set to .020 thou.
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Rotax 447 - .086 BTDC measured vertically |
Rotax 503 - .069 measured at a 30 degree angle |
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Rotax 582 - .078 BTDC measured at an 18
degree angle |
Rotax 618 - .059 measured at an 18 degree
angle |
Caution: Whenever doing the ignition timing always check the
triggers for continuity to make sure that they are not grounding
out. The red trigger should measure 50 ohms while the red/white
rigger should measure 130 ohms.
To do an Ohms check on the CDI system refer to service bulletin
999-695 which has all the OHM measurements to troubleshoot the
Rotax "E" box.
WARNING:
Do not cranks the engine over while the spark plugs are not
grounded or you could blow your "E" boxes!
PreFlight Check of Ignition:
You can do a quick preflight check of the ignition by bringing
your engine up to 3,000 rpm and turning one ignition off then the
other - you may notice a drop in rpm on one side and a gain on the
other this is normal - a drop or increase in the tach reading does
not indicate a problem with your ignition! |
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