Stumped here.. 85 FLHTC .. hook up the battery and try to start it, starter works but immediately the battery wants to light on fire. Like it heats up, starts to smoke, the positive lead gets amazingly hot until I unscrew the lead. It's fine with just the battery hooked up and with the ignition on, it only happens once I hit the starter button.

I bench checked the starter, I even took it to a local starter rebuilder shop and they checked it, it's fine.
I removed the positive cable, cleaned and inspected it completely, it's good.
I cleaned all the connections in the starter circuit.
I removed the solenoid, cleaned it cleaned the disk and connections. One thing of note is the the solenoid had some oil in it, I guess some oil is seeping past the seal from the primary, but I cleaned it and bench tested it, both in my simple minded logical way and as per the manual, I think it's good.

Fkin stumped here and I would appreciate any ideas. I believe the problem lies in the starter circuit so starter/solenoid/cables. I cant think of anything else that would turn the battery into a welder.

Thanks

 

You most likely need a starter Solenoid. I doubt you can repair the one in there. The contacts are welding on contact.

 

And ground wire off the battery, to the starter install bolt locks like what? Same with contacts on the starter solenoid and the plunger ring as well.

Hence do you have a good contact for the ground wire to the starter surface, not painted over so cause less then ideal contact, or the starter bolt channel threads surface corrode and not getting a good contact there as well.

Hence positive current side of the math may be fine (if battery is good as well, and will pass am amp load test/solenoid plunger contact ring and contacts are not burn to hell), but if ground side has a problem, then starter motor does not get enough current to spin it, and starts the melt-down problem at the battery and cables when using the starter.



The other one, compression on the motor increased, and without compression releases for the cylinders, standard starter has no chance in hell spinning the motor to start with. Even with high torque starter, may need to change the starter pinon to basket gear ratio, to give the starter a chance on a higher compression motor without compression releases.

Devil in in the details, so some photos of the above areas, as well as testing the amp load on the battery to make sure it still good and battery is being fully charged, will go a long way to figuring out the problem.

 

Great answers, thanks to you both. I suspected the solenoid.

Useful information I didn't realize mattered until I read your reply Dano is, the engine is a high compression Ultima with relief valves. I have on a few occasions attempted to start without pulling the relief valves ( I assume the PO has as well). This could have contributed to the issue.
I'll give the ground wire more attention, though it's completely clean the bolt thread is suspect. I'll be more careful to pull the valves before throwing money at a solenoid.

Thanks to you both.

 

Not hard to rebuild your solenoid, since its really just the disc on the plunger, and bolt head the other side contacts that can be cleaned up,
but since the price of some of the re-buld kits is close to just getting a new solenoid to begin with most of the time*, if not geared up with lathe and mill to do the clean up of the surfaces on the old parts end of contact bolts and plunger disc surface), just replace the solenoid with a new one.

Shipping cost is a touch over the top, but price is right for the parts needed to rebuild the solenoid.
Plus bronze for the plunger contact ring, and will last longer that a zinc plated one instead.
https://www.bmikarts.com/-Starter-So...65_p_5419.html

As for starter motor, would pull it apart to do a quick check of the armature wires to make sure none are burnt, the commutator pads and clean out between them, and make sure that the negative side of the brushes to the motor case is still a good contact, since problem may be the ground side of the math back to the battery negative post the problem at hand.

And don't forget to have the battery amp tested, since could still be good voltage, but plates are worn out and battery does not have its full amperage load isntead.

Note, if battery is a agm and less than 5 years old, I did a write up on fixing any dry cells is may have.
The low down, pull the fill plugs on the battery that will be under the sticker lable, fill the battery cells each with distilled water until the water level just comes to the top of cell top of plate each cell (don't bring the water up to bottom of fill plug like you would in a wet cell battery), then give the battery a few hours for the matt's and acid paste to absorb the added distalled water, and bob's your uncle with battery back to new, no longer having dry cells problems.
Note, some fill plugs can be a PITA to remove, but need to go back after the distilled water, to reseal up the cells in the end.

Hence agms work just like normal wet cell battery, but instead of water acid mix being fluid, its a water acid gel form so it can not splash instead.
The glitch, is the gel that can dry up from being over charged as a cell dries up faster than other cells to be over charged, so the distilled water trick works to re-mosten the gel, with the amount of water being added, just enough to re-moisten the gel, not leave standing water in the cell after the fact that can freeze to cause expansion problems isntead.



If wet cell battery and not longer will pass an amp load test, may be able to de sulfate the battery plates to bring it back, but most of time if battery is say older than 5 years, lead plates have cycle worn to the point that your fighting a losing battle instead. Hence may be able to desulfate the cells, but in the process with the cells plates already close to be eroded out from use, not going to be anything left of the plates after the desuflate process.

Hence way battery works, is as it being discharge, the water/acid in the mix will sulfate to the plates,and when you charge the battery, that acid is dissolved off the plates and back into the mix. With either dry or wet, the water evaporate out due to heat over time (why you check the water in a wet cell and adding water to the gel in a agm helps to re-mosten it), and each cycle of the discharge and recharging, does erode the lead plates a touch each time; until the lead plates are gone and the battery will not longer work.