QuestionI recently bought an ultra-light that has an 82 Rotax 277 2-stroke single cyl. It hasn't run for a while, says previous owner. I am trying to acquire spark to the secondary with no luck. I do have a pulse that will light a 3.4 watt 12 volt test light on rotation with mag. switch open. Do I also need a steady 12 volt signal back to the external coil for it to run? Or does the pulse fire the secondary coil to the spark plug?. Ohms values at the coil are within specs, but due to the age of the engine I have another coil ordered and am installing it. I did find the wiring diagram for the Rotax 277 and printed it off line. It shows a non battery ignition system and a battery ignition system. The wiring to the primary external coil is correct and the magneto wiring seems correct. I was an auto tech for 20+ years and have a year of auto technology behind me, but I have never wired or set up a magneto system or repaired one.
Frank Holbrook, Northern Idaho.
Please feel free to call me anytime
AnswerHi Frank,
A magneto system just takes the power from the mag coils and sends it to the ignition coil
when the contact points break open. The power from the mag coils does not
need to be very high as the ignition coil is a step-up transformer and
will increase the small voltage greatly.
Usually the problem is points not opening or dirty, burnt contact points.
On older autos the battery provided power to the points and coil, the magneto
just uses the same system with the magnetic flywheel and coils providing the power
instead of a battery.
The contact points are under the flywheel and fan.
They should open .012" - .015"
The arrow on the flywheel will align with the mark on the engine case
just as the points break open if correct. About 2mm BTDC
Being a two stroke the engine seals must be good too in order
to draw fuel into the cylinder.
Luck!
WS
------------------
