503 Electrical Fault - Help Please!

[salem]

I have an electrical fault on my 503. I ran the engine 3 weeks ago and she ran fine. On Saturday I tried to restart her and she was dead as doornails . I checked the fuel system, took the carbs apart, cleaned the filter, and checked the pump. I can definitely eliminate the fuel system as a source of the problem. There is good compression on both cylinders, so that area can also be eliminated. This leaves the electrical system. I first looked for the obvious faults. I tested the ignition switch, and it is OK. I visually checked for broken wires, dry joints etc. but could not find anything. I checked the spark plugs and they are perfect. However, when I checked if there is a spark (perhaps I should have done that first ) there was none.
I am lost! Where do I begin to check the electrical system? The Rotax manual gives only a perfunctory description of the system and I find their wiring diagrams inadequate.
Help please!!!!!!
P.S. The system is basic. I do not have any instrumentation, batteries,
lights, or electric starter running from the engine

[Duck Rogers]

......I tested the ignition switch.........

You mention "switch", not "switches"
Is this a single ignition, or dual ignition? or is it a dual ignition with both mags wired into one ignition switch?

However, when I checked if there is a spark.....there was none

Remember, you gotta give it a good yank to get the rpm up over 300rpm or so, otherwise you're not gonna see any spark AND I hope you had the plugs grounded to the casing when you tested for spark

[salem]

Hi Duck

1) Two magnetos one switch.
2) I yanked so hard my arm nearly came off
3) Yes I did ground the spark plugs before pulling the chord to check for
a spark.

[Miskiet]

Hi Salem,

Check the post on "Mag problem 582" lower down in the tech section. 582 and 503 uses the same ignition system. If you've got access to a multimeter you can check if you're systes reads OK.

Try and start with the obvious easy things - mag wires earthing against frame somewhere? Loose connections?

Hope you find the fault.

[Duck Rogers]

I presume this is a dual ignition, dual carb version of the 503.
Like Miskiet says, check the obvious things first, with a multimeter if possible.
But....if both sets of plugs are really dead with no spark, I would suspect the mag switch or the shorting cables that are connected to the mag switch. Check that they are not grounded, cos that's how the ignition is switched off...by grounding them. It will be unusual for both ignition coils to flake out at the same time, so, probably a common fault.
Also, the charging coils on the generator stator are independant of each other for both sets of ignition coils so, again, it's unlikely that both of them k@kked at the same time.
A sure-fire way (in more ways than one :D ) to check for spark is to hold onto the end of the plug lead and give the pull-start a yank. You'll know quick enough if it's alive or not :D 'cos sometimes it's not easy to see the spark.

Are you SURE that fuel is getting to the plugs? Have you checked to see if the plugs are wet or flooded with fuel after yanking the pull-start a few times?

.......best I can do for now. Keep us up to date.