GaSo Posted March 19, 2009 Share Posted March 19, 2009 Hello, I seem to have a problem with my charging system. At idle, 2000 RPM and everywhere in between, my bike just isn't charging the battery. So, I'm trying to figure out where the problem lies... I've got the Haynes manual (terribly inadequate), the XS360_400 manual from the Service Manual link (not terribly explicit), and the 82 XS400 Seca manual (great, but not terribly applicable). From crossing these references against each other, I've come up with the following for an 1981 XS400H: Any bike, with the engine running at around 2000-3000RPM, you should have about 14.5V across the battery. I do not, too low and drops as the battery discharges... Next, check the alternator. You have a stator and a field coil. The stator is three stationary coils, depending upon which manual I check it says they should be .49 or .72 Ohms, roughly +/- .1 Ohms. So, roughly, .4 to .6 Ohms, or .6 to .9 Ohms. Mine is roughly in that region, at .7 Ohms...as in, OK with one manual, NEEDS REPLACED according to a diff The field coil is the coil that swings around, generating AC current which the rectifier cleans up into DC. Mine is roughly 4.1 Ohms. Depending upon the manual, either 4 Ohms or 4.5 Ohms, again with a +/- range that basically means OK in one manual, NEEDS REPLACED in a diff manual Next, if you have a mechanical voltage regulator you can run some tests to find out if she is A-OK. Mine is solid state, so according to the Haynes manual "it is likely the problem"...thanks, that helps a lot. According to the 82 Seca manual (by which time apparently Yamaha had combined the rectifier and the regulator into one unit) I should be reading less than 1.8V in parallel with ground through the voltage regulator, through the field coil...at least I assume I'm supposed to leave the regulator plugged in, the Seca manual is less than explicit. I read about 11.8V with my battery at about 12.3V (a little low I know). So, voltage regulator problem? I bought two used off ebay, and all three show 11.8V across, so I'd guess that the problem is actually me understanding the manual...or I that just bought two bad solid state voltage regulators? The final check is the rectifier, which is the most straightforward: I just set my meter to the diode-check setting and make sure I got a reading around 700 on each of the single diodes, and 1400 on the two in series (.7 volt drop = normal). Rectifier is A-OK. So did I get burned on two bad solid state regulators? Looks like the wiring is the same as on the older XS400, but the electronics are newer. So I could theoretically take an old mechanical regulator and use it in place of my three bad solid state regulators? Or is my field coil bad? Or is my whole alternator system out of spec and needing replaced? I'm stumped!!! Link to comment Share on other sites More sharing options...
Moderator drewpy Posted March 19, 2009 Moderator Share Posted March 19, 2009 could be a bad battery not keeping charge thus affecting the alternator. It happened on mine and took me ages to suss (I even changed the voltage regulator) the battery was only 1 month old. now it charges a peach Link to comment Share on other sites More sharing options...
GaSo Posted March 19, 2009 Author Share Posted March 19, 2009 I asked my pops and that was the first thing he said too...The guy I got this off of said the battery was less than a year old, but...it doesn't seem to want to hold a charge. I've been blaming the POS charger I have...but all signs seem to be pointing towards the battery! Thanks for sharing your experience. Will replace and update the thread with my findings. Link to comment Share on other sites More sharing options...
GaSo Posted March 24, 2009 Author Share Posted March 24, 2009 Finally had a chance to work on the bike today, sure enough with the new battery, holding 2500RPM results in 14.5VDC! One thing I noted was that at 1250RPM, the charging system is putting out much less, looked to me to be about 12.7VDC, and the reading would peg out at 14.2 or whatever from about 2000RPM up, but below that it would ramp down to a low of 12.7V at 1250RPM? Sound about right? Also, the battery was shipped dry. I filled it with the electrolyte, and let it sit for a couple hours as per the instructions, topped up electrolyte. Then put it on a small charger ($35 for a new 1.5A max, battery minder designed for smaller batteries like this) for a day or two (recommended at least 10 hours). The next day, the electrolyte level in one of the cells was very, very low...where the hell did it all go!?!? I filled it back up with electrolyte instead of distilled water, as the instructions didn't mention wtf to do in that case...who knows, who knows...it seems to work fine now, I probably ruined it, $60 bucks for a good napa battery...sigh... Still don't have the left cylinder firing correctly at idle, but that'll go back in my original thread... Link to comment Share on other sites More sharing options...
WallyWales Posted March 25, 2009 Share Posted March 25, 2009 FWIW those type of batteries are notoriously short lived, and with the odds of putting a bike on its side its better to pay the $20 dollars extra and get a sealed type battery. Safer for the internals of your bike and it will last a lot longer than one that you have to fill and charge. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted March 25, 2009 Moderator Share Posted March 25, 2009 Finally had a chance to work on the bike today, sure enough with the new battery, holding 2500RPM results in 14.5VDC! One thing I noted was that at 1250RPM, the charging system is putting out much less, looked to me to be about 12.7VDC, and the reading would peg out at 14.2 or whatever from about 2000RPM up, but below that it would ramp down to a low of 12.7V at 1250RPM? Sound about right? that's about right, I can tweek my electro mechanical volt regulator to out put more but then it'll won't last as long. Link to comment Share on other sites More sharing options...
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