View Full Version : 79 commuter te390 electrical issues

01-12-2023, 10:51 PM
Hey all! Noob here. I donít own a trike but am working on a 79 commuter te390 for a friend of mine.

He said he was riding it in his driveway and it just died and wouldnít start back up. Convinced he blew the motor, he pulled it out of the chassis. Enter, me. I took the engine to my house and found the key way on the flywheel to be broken. I put a new one in and that is good to go. I hooked up a battery and turned it over, only to witness something I had never seen before. No spark while cranking the engine, until I release the key, at which point it will spark once usually, sometime 2-3 times before the motor stops spinning. Someone was in here messing with the wiring, as there are naked terminals, terminals with clips but no wire coming out of them. I tried to upload pics but was unsuccessful.

Iím curious if any of you have any ideas where to start. Iím going to test the key switch by bypassing it. After that, Iím kind of at a loss. Bad ground? Bad coil? Points? Does anyone have a wiring diagram for this beast?

Please help! Trying to get this thing done so we can rip it on the ice before itís gone.

Thanks in advance!

Homeless Dave
01-13-2023, 03:21 AM
I’ve never dealt with one of them, but I’ve had that issue. I’m a Mopar guy and up until the late 70s, old mopars had a ballast resistor. It had two circuits,, one for engine crank and one for it to stay running. When they go bad they will have the same problem you have, only have spark while cranking. Those style systems are so the full 12 volts goes to the coil for better spark, resulting in easier starting. One you let go of the key, voltage drops down. I’m assuming your situation is something similar.