sliverstorm Posted March 16, 2009 Share Posted March 16, 2009 I'm working on an '87 FZ600, and I'm trying to figure out what exactly is the matter. I think it's either a short or the alternator, but I'm not sure- basically, it dies when it's running normally, and when I tried to fire it up a few times today it stopped working. The first time it started, I stalled it on accident, and couldn't start it again, and the battery read ~2V. I jumped it to a car battery, and it started up and would keep running until you disconnected it. At first, remove the jumper and it just died. If you waited a while before disconnecting the cable, it'd keep running for a bit and die. It's either the alt not charging the battery, or a short draining more current than the alt can supply. My very first thought had been, measure the voltage while it's running, but that first time when I tried to measure it, I couldn't tell if it was 12V (i.e. battery) or ~14V (i.e. alternator) cause the meter I was using is crummy. My current thought is charge up the battery, and either leave it in the bike overnight and see if it drains, or charge said battery, run it, and watch the voltage. Any tips, or recommendations of good places to look for shorts? Also, if it turns out the bike is just draining the battery while it runs is there a better way to test the alt itself, and make sure it's not rust or corrosion etc in the wiring to/from the alt? P.S. the bike was running fine, then it sat for a while and this cropped up. P.P.S. tried push-starting it, didn't work. This suggests alternator, but I'm more familiar w/ cars than bikes- on a bike, will push starting it work if the battery is gone/dead? Link to comment Share on other sites More sharing options...
wild foamy Posted March 16, 2009 Share Posted March 16, 2009 push-starting a bike with a dead battery usually wont work, i had the same problem with my Jawa and unless they have power in the battery it wont spark, on small bikes with magneto ignition you can get away with it but not on these bikes with electronic ignition... Link to comment Share on other sites More sharing options...
Madison Motorsport Posted March 16, 2009 Share Posted March 16, 2009 I doubt it will be the alternator if the bike is running for such a short length of time before failing. It will either be a stuffed battery or a drain somewhere. Although, I've not come across anything that will drain a battery completely within a few minutes I must admit. Link to comment Share on other sites More sharing options...
sliverstorm Posted March 18, 2009 Author Share Posted March 18, 2009 Ok, I just checked the resistance across the battery connectors. .4 ohms. that's 30 amps of current flowing when nothing is happening It fluctuated a little depending on where I was poking, but only by an ohm or 2. Also, this massive short only appears when the key is switched to the 'on' position. This also easily explains why the voltage is not 14V when it's running; with that much draw, even a good 14V output would fall flat on it's face. Any ideas how to find an electrical short? Link to comment Share on other sites More sharing options...
Moderator mervin Posted March 18, 2009 Moderator Share Posted March 18, 2009 I had the same with a bike after it was laid up,the battery was dead on it and would not hold charge had you charged the battery before the first attempt? cos it sounds to me like a flat battery, one way to see if you have a big short is too charge battery off bike and see if it sparks badly when you reconnect, merv Link to comment Share on other sites More sharing options...
sliverstorm Posted March 18, 2009 Author Share Posted March 18, 2009 Well, the short only shows up when the key is in the 'on' position. Would a dead battery explain the voltage dropping even while the bike is running? That's why it dies, is the stator seems unable to keep up with the load. I tracked it down to a certain fuse. The irony is, at .4 ohms, it was drawing ~30 amps- it's a 30 amp fuse, so it was *just* too little to blow. Anyway, I thought I had it pinned down to the instrument panel, so I took of the fascia and tested unplugging those connectors, but just when I thought I had it, my readings on the multimeter went wacko. Possible it's a short in the harness between 2 wires, and me moving the harness has affected them. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 18, 2009 Moderator Share Posted March 18, 2009 I suspect the regulator / rectifier, you may find This useful Link to comment Share on other sites More sharing options...
sliverstorm Posted March 18, 2009 Author Share Posted March 18, 2009 Thanks for the input guys! I found it, by the light of the moon and my AA flashlight. The plug to the rectifier was partly melted. It seems like what must have happened was water shorted the connections, and 30 amps basically melted the socket and destroyed the terminals. The short circuit may or may not have been causing problems; more importantly, since the power line from the rectifier was toasted, the bike wasn't charging. Hooray! Now let's just hope I don't have to replace the rectifier, ever. I had to do some hacking, cause the plastic was actually solid in some places. as in, the plastic liquefied, mixed and set. Link to comment Share on other sites More sharing options...
lyenga ronnie Posted April 7, 2009 Share Posted April 7, 2009 I suspect the regulator / rectifier, you may find This useful My name is Ronald. I work in a mobile telecommunications company here in Kampala, Uganda. Am an ardent fun of Jawa 638 However, my bike has a problem with the wiring system It starts fine. From memory you push the key in hard to turn the ignition on and then turn it with it still pushed in to work the lights. First, the ignition key can only be left at 0 for the bike to move. So this means the lights will not work. But when you turn the ignition key to 1 for the lights to work, the engine goes off and the battery is drained The problem I have hear is that mechanics in Uganda are not well-versed with jawa technology The switch was checked for a possible leakage. All wiring in the switch works fine Recently a mechanic told me it could be a problem with the alternator and Tout Kindly advise. I have a feeling you have dealt with a similar case before Please also help with with a user manual or details of the wiring system that could be helpful in sorting out this problem Link to comment Share on other sites More sharing options...
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