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Dead electrics, 97 SRAD 750, Help!

2K views 12 replies 4 participants last post by  Raging Tweety 
#1 · (Edited)
I've been working on an old 97 SRAD on and off for 4 years. The bike is on a race stand in my heated porch and hasn't moved. I have almost all issues with it fixed, I've replaced the oil hoses, fixed the fork seals, completely rebuilt the brakes and changed the lines, etc. But ... and I know it was aspirational ... I thumbed the starter for a fraction of a second and all electrics on the bike went completely dead :banghead (never even turned the motor over, but no burning smells or nasty sounds were noticed when it happened) -- and weirdly, this isn't the first time...

The first 3 times this happened (two of them last summer), the the electrics mysteriously came back on -- nothing I did -- some 12 to 36 hours later. :wtf Right now electrics are off -- no lights, no instruments, no parking light ... no sign of life at all. Couldn't be more dead if I took out the battery.

Here is what I've done/checked:
*The battery is fine
*Checked the main fuse and it's fine -- swapped it just in case.
*I inspected the connectors (opening them and looking) and didn't see obvious issues -- including the big ones on the left side of the bike, as well as those to the starter relay and regulator/rectifier. The bike hasn't moved, so I have no reason to think connectors would be the issue anyway.
*Inspected visible wiring and found nothing (admittedly a lot of it is wrapped with electrical tape, which could in theory be hiding something).
*I swapped out the starter relay -- this didn't help.
*The motor can be turned over by hand (rolling in 6th gear). Last time this happened, the bike recovered and the starter turned the motor over just fine with no further issues until now ... I thought at the time it was just a glitch from sitting that resolved itself.

Whatever is the cause:
*It must be something that is able kill all electrical power to the bike even with a good battery connected, and yet might come back on its own after sitting for some hours. (What components can do this? Can a bad rectifier do this? I don't know ... I thought it might be the starter relay but it wasn't -- I've attacted a wiring diagram for my bike)
*It seems to be instigated by the big power draw from the starter after the bike has been sitting for months.

Even though I can't see how they could cause the issue I checked the fuses in the fuse box, they are fine. I'm stumped. I searched the forums and didn't find any problem exactly like it. Does anyone knowledgeable know what might be the problem?
 

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#4 · (Edited)
When the electrics were all working, the lights were on, the instruments alive, etc. I thumbed the starter, and all electrics died, but mysteriously came back on (for the first two occurrences) after the bike sat long enough (hours to a couple of days). I didn't try to bump start the bike in 6th, I just wanted to be sure the motor wasn't seized in case I had a more serious issue that made the load on the starter motor cause electrical misbehavior. I've checked really obvious things: the battery is ok, wiring is still connected to the battery and everywhere else, connectors looked ok ... I giggled the wiring as I took the connectors apart to inspect them. Thumbing the starter shouldn't cause wiring to disconnect itself anyway I would think.
 
#6 · (Edited)
That's right, the dash lights never came back on ... everything electrical appears completely dead. The battery reads 12.5v on my multimeter. I've pulled the regulator/rectifier off the bike now and I'm checking it with my multimeter according to my Haynes manual. It is suspect, but I have only discovered conclusively ... I need new batteries for my multimeter :banghead Off to get them ... back in 20 min. Do you know if a dead rectifier/regulator will make all the electrics on a bike seem dead?
 
#9 ·
Yes, I replaced the main fuse on the starter relay as you say ... I have 4 or 5 of those 30 amp fuses around ... all working as far as I know. A dead fuse would stay dead until fixed I would think. The reg/rec can't be the issue either (even if it does turn out to be dead) if that won't suddenly kill all power to the bike (which is kind of what I figured, but I didn't know for sure). I really don't know with 100% certainly what components other than the main fuse will kill all signs of electrical power on the bike -- which is half my problem diagnosing it.

If it isn't a component, maybe it is a short -- (all power died instantly when I pushed the starter-button). Virtually all the wiring has been wrapped in electrical tape by a previous owner. I'm sure he had his reasons, but it is going to make a full and thorough check of the wiring a real pain.
 
#10 ·
I had a '97 r 750 last summer.

On my first ride I was in a left turn lane stopped. My hands where resting on the gas tank.
The green arrow came on, I reached up for the clutch and the throttle- bike went dead.
I pushed it over to the sidewalk- freaking out 'cause I just bought this cherry 750, and it suddenly went dead.
I looked things over- and grinned.
I had bumped the kill switch on the Rt clip on!

You didn't mention it- so I thought I would bring it up- even though I realize it's probably not the problem either.

Good luck- awesome bikes-
 
#11 ·
Perhaps I've missed something, but the observed behavior strongly points to a dead battery. Measuring 12.5V on the terminals doesn't necessarily mean anything. The battery might have enough charge to drive the lighting and other electrics, but not enough to operate the starter motor, which draws a heck of a lot more current, especially at startup. When the starter tries to draw the current it quickly depletes whatever electrolyte remains around the (probably mostly-sulfated) plates and the battery goes completely dead. A few hours later more electrolyte has permeated through the matting around the plates, allowing some charge to be drawn again and the battery seems to miraculously come back to life.

Try measuring the voltage on the terminals before and after you've switched off the ignition. If, after switching on, you still have 12.5V at the battery, but the bike still seems dead, electrically, then you probably have other problems as well (but the battery might still be dead). If the voltage drops, as soon as the battery tries to power on the lights, then it's surely dead and must be replaced.
 
#12 · (Edited)
Perhaps I've missed something, but the observed behavior strongly points to a dead battery.
And to my considerable surprise, we have a partial winner here. When I checked the voltage this morning it was a 12.4 ... a drop from last night. This made me think LoneStranger1969 might be right about a short which could be causing a drain on my battery ... and this *might* be the case ... I'm not sure yet. To see what I could find I started checking voltages on wires, and finally (after many checks of ground and live wires) I worked back to the taillight (wired to on at the be 'on' with a paperclip at the connector that normally hooks to the ignition ... the equivalent of being in park) I checked the positive lead (the brown wire) and found it was live, and I checked the ground to taillight (black with a white stripe) and it was fine too ... but the :cursing taillight was still off. Of course the only way this makes sense if if there is insufficient amperage from the battery to even light up a single taillight. I dug out my charger to refresh the battery (which I'd only charged about a month ago, in theory, to maintain it) ... the taillight goes on immediately. Reassemble the connectors, wait a few minutes, turn on the ignition and poof ... the electrics are all back :cheers

I may still have a short or something draining my battery, or maybe the battery has issues and is draining itself. Either way I'm much closer to a solution than before, and best of all, perhaps I'll be spared having to fit my bike into one of those damned blue recycling bags, and lugging it to the corner of my driveway in defeat :wink2:
 
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