Bike went up in smoke last night..

Well hopefully I grabbed your attention.. The bike did indeed go up in smoke, luckily it wasn't a fire. I do need tons of help trying to figure this out though. So stick with my and share in my misery.. You all probably hate i cut up the xj and get a bit of joy when i fail anyways. So here's my story..

Was out on the bike, probably about 20 miles into my ride last night and suddenly all power dimmed, then cut off, i coasted about 10 feet before i realized smoke was pouring up from under me. I jump off the bike and thankfully no flames, just TONS of smoke from the battery cooking itself. Bye bye $150 battery.. The battery cooked like that for about 5 minutes. It was late, and dark and by the time my wife towed me home I only had time to disconnect the battery and do a quick once over.




So now that daylights here i went for my first suspicion... The rectifier went and i over volted the battery via a bad diode or something. (Not horribly familiar with the rectifier diodes and wiring) I get no further than taking off the rectifier than noticing that the brown pin had worked its way out of the connection. I can't imagine it was making any contact to complete its path at the point when this happened.




First off, I would like to test the rectifier's diode but i can't find the link to the procedure. Second I wanna be sure as hell I figure out what this is before I put a $150 battery in here again. So I'm calling on all the experts here to really help me get through this. The bike has been running find and I probably have about 75 miles on since I rebuilt it. So I'm not sure why tonight this happened, and not sooner. So please throw all the knowledge, criticism, and ideas my way please and thank you!

 

That switched voltage on the brown wire is an input to the regulator to sense battery voltage. As the voltage rises to indicate battery full charge the current applied to the field coil (rotor) is reduced to limit the output of the AC Generator, and consequently the charging current to the battery. With no connection at the brown wire you were at full charge, which will seriously overheat the battery.

Here is a correct drawing to test the diodes and the rest of the charging system:

 

"yamaha pocket tester" .. I'm assuming this is a multimeter on the continuity setting? Obviously can't test the charging system until a new battery comes in but the second half of that procedure seems like a bench test.

 

Yes it is a multimeter, but the old less expensive variety. If you check the diode with a more modern multimeter in the "diode" mode you will notice that the polarity of the leads is opposite of what is depicted in the FSM literature. It was common for older meters to reverse the polarity of the leads, which resulted in the polarities noted in the chart. As long as the diodes read approximately 500 ohms in one direction (diode mode), and open in the other they should be OK.

 

Bummer, lucky though it wasn't a Tesla............

Good info from Rooster.

 

So assuming the rectifier tests fine, this brown wire seems like the smoking gun to this problem? I ran over the harness and didn't see any other visual problems and all grounds appeared good. Just want to make sure I go over everything before putting another $150 battery in.

 

May not hurt to run through all the charging system tests since they're fairly simple to do just to make sure. I agree that likely the lack of connection on the brown wire is your smoking gun. No pun intended haha

 

For sure will once the battery is back in. Can't test it until then, want to make sure to cross everything off my list. (Or everyone else's list because my list is apparently inadequate)

 

here are my findings according to the chart using my 'yamaha pocket tester' (multimeter) :

D1 - 545
D2 - 527
D3 - 532
D4 - 543
D5 - 547
D6 - 544


Not sure if theirs anything else to bench test but this was my results. The only tested one way.. if i had the black and red leads flipped on my multimeter i wasnt getting any reading. took me a minute to figure that one out.

 

should be good by the numbers you posted . didn't you drag the rectifier on a test run? could be what pulled out your wire

 

Possible. But when I rewired it,it did not appear to be that way. The pin retainer on the brown wire needed to be bent out, but it now snapped it and is fully seated.

 

Got my new battery in, tested everything in the charging system. although I didn't get up in the revs tooo much (very loud bike). Anyways, v2 was .84V with main switch on. V2 than rose gradually.. the highest I got it was about 4.9 volts but it seemed like it wanted to climb if i would pin it. I'd say throttle half way was about 4. As for V1, it was in the high 13's upon start but stablalized at 14.4V when reving and then in idle it hovered about there.

Everything sound okay according to the tests or should i dig deeper?

 

Seems to me like you were just waaay overcharging the battery. Get that wire back in where it belong, get a new battery from Walmart, and go ride.

 

Good read, and be very happy the battery didn't bust on you...WOW so lucky...glad that worked out for you and you were able to trouble shoot it down to the "Brown" wire.

 

don't some of those batteries have protection circuits built in?

 

Yeah--- see how well they work ?

 

his didn't have a protection circuit, obviously. that whole line is discontinued, i wonder why http://www.batterytender.com/new-batteries
think the new ones will?

 

I'm thankful whatever it was happened in the battery and the battery only.. seems I cooked it for sure, brown wire was the culprit based on my findings. I'm not exactly pleased with the battery but it offers the CCA in a size i can hide where I NEED(want) to hide it. Maybe the new one has it maybe not, Wish i could go with one that did for sure? At any rate, Some miles in the saddle to get the battery up and charged will tell.

Speaking of circuits, Not sure of the best type to maybe monitor this situation? a temp sensor seems maybe it could be rigged up... I dunno just kinda thinking of a way to maybe monitor it, temp, voltage, whether its charging, simple LED yes no style. I'd imagine if i get past 10 miles this time I SHOULD be good.

Someone had mentioned silicone on the back of the connector so the plugs can't rattle loose out the back side.. I think it would server its purpose but might make it hard to work on in the future? Any insight?

 

Check to see if the little barb broke off. That really shouldn't have slipped out the back that easily.

 

ebay "voltmeter motorcycle" bunches of them. that's what you want to monitor