Rotax point ignition wiring diagrams
Under no circumstances should a tachometer be connected to the two black leads. Another problem encountered with the ignition system is with the ignition suppressor box. This box is generally located on the Rotax starter recoil, is a brass color, with two leads, a brown and black, coming out and joining into the ignition system.
When this box fails it can cause a complete loss of spark to one or both coils. A way to quickly check the box is to reverse the leads, if there is spark one way, and not the other then the box is still good. If the box does happen to fail on you, it can be simply disconnected from the system and your spark will return.
It is suggested however that you replace the box, at the earliest possible time as it does play an important role in extending the life of your engine.
The final problem encountered in the ignition system of the Rotax engine is in the use of an ignition switch which simply joins the two black leads from the magneto together to shut the engine off.
This is not the recommended switch. In all applications the proper switch is referred to as a four pole switch. This switch allows both black leads to be fed into one side of the switch, while the other side goes to ground. When the switch is operated to shut the engine off both coils are grounded, ensuring a complete ignition shut off.
Bing 54 Carburator troubleshooting
Carburetor: In most applications the Rotax engine uses a Bing 54 carburetor. In adapting the Bing for ultralight use several problems have been encountered. One problem that has been reported is the failure of the retaining clip of the jet needle, located in the carb slide, due to vibration and fatigue . This failure allows the jet needle to fall down into the main jet cutting of the supply of fuel to the engine.
The engine still runs but at an idle. This should be an area of regular inspection.
There are two vent tubes located on the side of the Bing carb. Do not connect any additional hoses to these vents, or vent them outside an enclosed engine installation. By venting outside the engine cowling you create two different air pressure areas, that of the outside air, and that of the air inside the engine cowling, which can effect you fuel mixture.