Motorcycle, battery, starter question.

I have a very limited understanding of electricity so let’s get that out of the way.
I have a 1993 Harley Sportster that I bought new. It started life as an 883 cc. displacement. After about one year I had the dealer that I bought it from install 1200 cc. cylinders and pistons. They asked me at the time if I would like the heads milled for a higher compression ratio and I said yes. There is no indication on the receipt that they did this but I am pretty sure they did. It really needs high octane gas and I’m convinced that the compression ration requires it.
In 1993 there was a separate part number for an 883 starter and a 1200 starter. I’m still running the original 883 starter. I’m assuming the 1200 starter is “beefier” i.e. “torque-ier.”
The problem I am having is that the negative terminal is getting excessively hot, to the point that the lead from the negative terminal has melted and the plastic around it has melted as well. Everything is OK as long as the terminal connection is tight but for some reason the terminal connection is constantly getting loose and consequently getting really hot.
Could this be because I am running an “under powered” 883 starter instead of the 1200 starter? It seems like the larger displacement and higher compression might put more stress on the starter leading to overheating the battery connection but I really don’t know. When the bike is cold the starter spins the engine really well, when the engine is hot it is very sluggish but always starts.

I’m sure better gearheads will drop by soon enough, but here I go for a first response.

The battery terminal is getting hot because of high current. The starter draws the most current than (probably) all other components on that bike, combined, so, yes, the starter is causing the high current draw. I would at first, however, suspect a bad ground cable, perhaps corrosion inside the cable near the battery. I would like to think that the dealer would have recommended an upgraded starter if the 833 starter would lead to overheating of the wiring. I would replace the ground cable before I did anything else.

Edit: the bad ground leads to lower voltage, which means the motor must draw a higher current to turn the engine over. By replacing the cable, you might be OK.

Edit Edit: if you want to check, start the bike hot (starting slowly) and check the temperature of the cable. Then, stop the engine and run a jumper cable between the neg terminal and the frame and repeat. If it doesn’t get hot, then it’s your cable.

I know just enough to be dangerous.
With that said, You should have gone with the 1200, starter ad bigger battery amp hour rating and bigger cables.

Since you probably do have a higher than normal compression ratio. Your fuel should be Ethanol free and the highest octane you can find.

YMMV but that is best for your engine IMO. If $$$ is a concern, get bigger wires in their first so they can carry the current without over heating. Remember, a starter is almost a dead short until it starts turning, Major amp draw. How long that starter will last is just a guess on my part. Really big cables, a battery with a higher AMP ratting, the biggest you can fit in the space. Still cheaper than a new starter as I bet that is major $$$$…

There are other things you could do but this is where I would start if $$$ are a concern. Might check with your dealer and see what the conversion would cost. Just so you would know.

Good luck.

This is not normal, and should be an easy fix. Make sure all the terminal surfaces are clean – shiny metal. Verify that they can be connected tightly, to where nothing can be moved by hand. If something doesn’t tighten up properly, replace it or devise a way to secure it.

I was thinking of replacing the ground cable mostly because it seems unnecessarily short, making any battery related maintenance more difficult.

If it’s not getting hot when it’s tight but keeps loosening then I’d suggest lock washers or conical washers to help keep it tight.

Compression releases might keep it from having to working so hard.

Done. After I get everything tight and clean, it loosens back up, maybe from melting a little off the battery terminal.

BTW, the battery I have is awesome. I’ve had the bike 25 years more or less and this battery is the best one yet. Got it from the local Batteries Plus store.

It’s melting the lead?

This is a nitpick, but: You’re going to have a very hard time finding ethanol-free gas. Not only that, but ethanol can stand MUCH higher compression than regular gasoline (even E85 is at least 100 octane). It’s the only reason to run a racing engine on it, and it works pretty well.

The only reason to be wary of ethanol in an older engine is that it can deteriorate the rubber hoses used to transfer fuel, maybe the seals in the carbs. (checks when Harley introduced fuel injection) You’re gravity feed, unless you’ve converted to injectors. Replacing that line with one that can handle E85 should be a piece of cake, if you haven’t already. Carb gaskets are usually paper, but there can be rubber parts in it depending on the design. I’d ask a genuine Harley mechanic, but you’d probably be fine for E85 with just a line switch.

And yeah, if that terminal won’t stay tight, replace the cable with one that will. If it’s melting the lead, you’ve got a problem I’ve never seen before.

ETA: The loosening of the cable is probably from the vibration of the engine and a cable clamp that’s gone cone-shaped on the inside. The more you tighten it, the more it slips off the terminal. I’ve seen that before.

ETA2: Oh, and ethanol absorbs water over time. Drain the tank if you aren’t going to ride for awhile.

I have a 97 Harley Dyna Wide Glide. These old Harleys do have a tendency to shake their battery terminals loose. It’s fairly common, and I’ve had it happen on my Dyna.

Once you tighten it though, it should stay tight for a while. The terminals might eventually work themselves loose again, but they shouldn’t constantly get loose. If you have the problem once every few years it’s no biggie, but having the problem constantly is definitely not normal, even for these bikes.

If you have melted plastic, then I would suggest replacing the cables completely. Check the connector on the battery. With all of the heat and melting issues you’ve had, I will be very surprised if you don’t need both a new battery and new cables at this point.

I was under the impression that the 883 and the 1200 used the same starter. Maybe not on your year. If the starter feels like it is struggling then you probably need to upgrade it. Otherwise it’s probably ok.

My engine (1340) needs higher octane gas, and you are right, the compression ratio does need it. I can get away with 89 octane in mine, but definitely not 87. You can’t find ethanol free around here. As long as it’s not more than 15 percent ethanol it’s not that big of a deal. Once you get above 15 percent ethanol is when it starts to deteriorate the rubber hoses and seals.

Are we certain the the starter current is the culprit?

I don’t know anything about motorcycles. But on a car, the starter is on for such a short period of time that there’s usually not enough time for electrical connections to heat up to any appreciable extent.

This is my thought also. The cable should not get that hot in the brief time the starter motor runs.

I can tell you from personal experience that if you have a loose connection, the cables and terminals on a Harley battery will get very hot very quickly just from starting.

Once the bike is running, it doesn’t draw much current. Unlike a car, a motorcycle’s headlight is always on (required by law for several decades now), so you always have that, but otherwise it’s just the engine’s ignition system and a little bit for some other electronics. The starter is by far the biggest current draw.

Compared to a car, motorcycle batteries and cables are tiny.

On cars I’ve occasionally drilled a hole through the cable end and into the battery post, then installed a sheet metal screw to make good secure contact. I’d bet with a couple of such screws that puppy wouldn’t vibrate loose.

Harley batteries are the screw-on type. They aren’t the round posts that you have on a car.

They look like this:

I don’t know where you could fit an additional screw.

Thanks for the input everyone. I don’t think the battery cable terminal is vibrating loose. The last time I tightened it was a few weeks ago and I got it as tight as I could without stripping the threads out of the lead terminal. It was loose again when I tried to start it yesterday. I probably rode less than twenty miles since I tightened it. I think the loosening has something to do with it getting hot.

The lead terminal on the battery is a square post with two threaded holes, one vertical and one horizontal. The horizontal one is where all the lead melted away so I wrestled the cable around and bent the cable terminal to 90 degrees so I could fasten it to the top of the battery terminal using the vertical threaded hole. It should make better contact because no lead has melted away on that surface and will also allow me to check tightness or tighten the connection without removing the battery. I’ll see how that works out.

If the thermal cycling is what’s causing the loosing there’s bigger problems. I’d suspect interstrand corrosion at the connector or loose crimp on the connector. Probably behind some heat shrink tubing.

Maybe a connection problem inside the battery at the terminal as well.
If the starter current were the problem the positive side would be getting just as hot, if all other things equal.

Series resistance on a DC motor like that should decrease the amperage, which would also decrease the available torque at the starter.

Try tightening the bejesus out of it when it’s hot.

One consideration is the bike is a big air-cooled twin, and the starter is up front and under the forward cylinder exhaust. The whole thing might be running very hot.

Shit rattles loose on Harley’s all the time. I’ve never had a bike that more stuff fell of than my old Harleys.