Tech Assist: Starter engages; won't disengage;wires burn!

This has happened to two of my friends in the last week,one at York.One on a car ;one on a Harley. The guy goes to start the engine,it turns over real slow then when he shuts off the key,the starter keeps turning and the wires start to melt and catch on fire. The car guy had a kick panel catch fire and lost all the wiring behind the panel.
Both had just installed new staters because the old ones were turning over slow. Whatzzzz Uppppp ???????

 

Bad starter solenoids cause this problem.
They stay on and keep the starter engaged into the flywheel.
The constant current to the solenoid will burn the wires especially when they aren't a large enough gage wire.
If the starter engages into the flywheel but the solenoid isn't shorted. There isn't juice going to the solenoid and the starter spring is broken preventing the starter to retract from the flywheel. But since the wire got hot. It is either a shorted solenoid or a bad ignition switch causing current to constantly fire up the solenoid.
Oh Yea, don't forget to check the relay if the car has one.
It is routed between the ignition and the solenoid. They can go bad too.

 

It can also be the flywheel physically holding the starter drive out which will keep it cranking. I had this on one after the only change being the flywheel.

 

I've seen this on GM starters when the main cable turns, either because it is loose, or when the mechanic tightens it, and touches one of the terminals on the solenoid. When the vehicle is started, the starter wont stop cranking, even though the engine is running. Alot of noise and burned up wires, etc.
May not be the cause of your particular problem, but something to double check when you are installing a GM starter..

 

In both instances the starters had just been replaced with new / rebuilts,so I'm wondering if they didn't get the wires just right and either caused a short or a bad ground?