engine runs rough

[Slyfox]

a little update on this. I cleaned the plugs, they were quit black. started it up, and it ran very good on the right mag. left mag, ran like it was not on all 4. problem is in the ignition. I had my spare cdi and installed it on the left side. switch that is. not sure at this time which coils that one runs. will find out though. I have the rotax heavy duty manual so I have the wiring diagram for this. I replaced that cdi about a year ago with a soft start. the original cdi quit working when cold. installed that cdi and ran the same, so it is working. I am starting to think coil at this point. I need more time to dig in and find the problem. let you know.

[AvDES LLC]

Good to hear the troubleshooting is going well. If it ends up being a coil I HIGHLY recommend reaching out to Hal. He has a stash of them and will save you big bucks.

[Slyfox]

like I said I need to find out which side I'm working on, a or b. I know which side is which on the diagram not on my plane yet. going to rip the system off the motor mount and dig in maybe tonight. I was way excited that it turned from an intermittent problem to a hard problem. I'm sure I'll find it.

[Slyfox]

well it tested positive for a bad coil. I ordered one and I hope this is the end to this saga.

[AvDES LLC]

Great to hear you’ve isolated the issue. Keep us informed when the new coil goes in if the problem is solved!

[Slyfox]

the saga continues. I did put that coil on, didn't fix it. I got me a timing light and put it on t1 and it wasn't firing. checked t-2 and it was firing. what the heck. that's on the same coil. can't be the trigger it runs both on or should I say fires the coil with one trigger for t1 and t2(let me know if I'm wrong) . so back to the cdi module. this is the new one I got about a year ago with soft start. my thinking is this thing is bad. so what I'm going to do now is take the module I took out and put it in the freeze for an hour and put it on ice and take it to the airport and install it and hopefully be able to start the plane. you see it failed and wouldn't work until the engine has 2000 rpm. it is said it will start working if put on ice for a bit. this is a green label cdi. I will see if it will start and have the timing light on that plug. got me baffled for sure. I did check the ohms for the triggers, they are all the same so should have good wires going down to the triggers. wish me luck, cus that is what this is turning into.

[AvDES LLC]

sorry to hear the frustrations continue. It’s odd as a single coil is triggered by a single trigger wire from the cdi. If one of the plugs on that coil is firing, the trigger from the cdi is good. Have you changed out the spark wire and plug boot to see if those have an internal short? Napa auto parts will have some 7mm wire you can pick up for a few buck to make a test wire.