battery meltdown

[SpiderFJ1200]

I know what happened and why. I even have a spare starter relay, because the last time this happened I applied blunt force kinetic energy to it to fix it. This time, I'm just gonna use the spare. Sequence of events: tried starting my bike this morning and the voltage must have been low from sitting in the heat for so long. We've been having highs in the triple digits every day for the past few weeks. All of June. Well, I ran it out of juice and the starter seized, and once that happens nothing will make it stop trying to turn over until it is out of juice or the battery is disconnected. By the time I get the seat off the negative battery post is dripping down the side of the battery. I don't think I'll try and charge it back up. It's old. I'm gonna call it dead now. In the mean time, I'm having my support network run errands for me as my FJ is my only source of transportation.

[SpiderFJ1200]

I've been trying to find some source on why this happens exactly. Ohm's Law is V=I*R. So if the voltage goes down, the current should go down too. Any electrician able to explain how this happens?

[Old Rider]

Im not a electrician ,but strange that no fuse blew ? I know on my bike before i replaced the 2 brush starter trying to start the bike when hot the starter
sometimes could not turn engine over because the piston clearance gets smaller i think.I blew 2 gel batterys that way it sounded like when opening a bottle of campagne under the seat .After replaced the startermotor with the 4 brush type the engine turn over everytime when hot with no problems.
Here is a pic of a 2 and a 4 brush starter and how you can see the differense outside.

[racerrad8]

The starter seized or the starter solenoid/relay stuck and the starter continued to crank after releasing the starter button?

Randy - RPM

[SpiderFJ1200]

The starter seized or the starter solenoid/relay stuck and the starter continued to crank after releasing the starter button?

Randy - RPM

Correct. It only happens when the battery is almost dead. The starter relay fuses together, completing the circuit, so it won't stop trying to turn over until the circuit is physically broken. Turning the kill switch off, key to off, key out of the bike and it continues cranking. The battery in question is a larger battery than what is called for. An EXT20L with 310 CCA. The battery I just bought is an ETX15L with 220 CCA.

[RPM - Robert]

The starter solenoid/relay shouldn't fuse together even due to low voltage. The spring inside should disengage it once the starter button is released regardless of voltage.

It is fused together, then the heat caused by the loosest/weakest connection is where the most heat was generated. That appears to be your negative terminal.

Randy - RPM

[FJmonkey]

In smaller relays (like VF4, a common automotive item) the contacts can weld together. I have seen arcing cause the contacts to weld when I opened many failed relays. A relay can be found with a built in Diode that suppresses the arc. Or a diode could be added in line as well.

[T Legg]

Since this problem of the starter not stopping after the starter button has been released has occurred before and with a different relay I wonder if the starter button spring is weak and staying connected. I guess though if you turned the key off or the kill switch it should have stopped . You should break open the first bad relay you took off and see if the contacts melted together.
I would agree the battery post meltdown is likely from a loose battery connection.

[SpiderFJ1200]

Since this problem of the starter not stopping after the starter button has been released has occurred before and with a different relay I wonder if the starter button spring is weak and staying connected. I guess though if you turned the key off or the kill switch it should have stopped . You should break open the first bad relay you took off and see if the contacts melted together.
I would agree the battery post meltdown is likely from a loose battery connection.

The relay can't be taken apart without cutting through the metal case. However, a multimeter shows continuity between the two main posts. Which it shouldn't do. The last time I fixed it with a hammer, hitting it until it no longer showed continuity. So it's the same relay that previously seized. I have now replaced the relay with a new one so it shouldn't happen again.

[Motofun]

Another failure mode I've had happen to my '85 is the weak cheapo spring in the starter button can fail allowing the button to stay engaged.  Of course it's easy to just pull the button back out unless you've already put your gloves on!

[SpiderFJ1200]

Another failure mode I've had happen to my '85 is the weak cheapo spring in the starter button can fail allowing the button to stay engaged.  Of course it's easy to just pull the button back out unless you've already put your gloves on!

It never stays engaged from that, but I do have to pull it out after I start it so the headlight will come on.