View Full Version : Quick charging question. 1986 XV750

04-16-2016, 6:14 PM
Ok, I'll try and keep this quick. My bike (86 XV750) isn't charging from what I can tell. Now its either a bad battery or the charging system, I have not checked the output of the stator yet or done the rectifier test listed in the manual yet. But when I have the voltmeter hooked to the battery at rest it says 12.4 or close too…..when I start the bike it drops down to 9.5-10 during the starting then goes back up to 12.2-12.4 while idling…BUT doesn't climb at all from there at different RPM's. I tried 1000, 2000, 3000, and almost redline for a couple seconds to see. No change? Obviosly the output test on the stator and the rectifier test will say more. Could a bad battery prevent the reading on the voltmeter to actually go up during higher RPM's? I hate electrical!!
Just looking for any tips or suggestions that may help.

*Note. I have move the rectifier off the rear foot peg and added a ground wire directly to the frame in hopes of helping. This change allowed the bike to stay at 12.4ish at idle. Before that mod I didn't have it grounded for a test and it dropped down to 11.2-11.4 at idle.

Like I said, any tips or advice is appreciated. Have a dinner to go too but will check when I get home before heading back out to the shop tonight. Thanks in advance everyone!!

04-17-2016, 2:58 PM
*Test Details:
Multimeter set to DC Volts Reg/Reg connected
-Batt at rest=13.00 just off charger
=12.42 after running a couple minutes
-Batt key on = Trickles down from 12.45ish slows at 12.00
-Batt at starting =10.5 to 10.7
-Batt at idle = 12.05 to 12.08
-Batt at 3000rpm = 12.27 to 12.29
Multimeter set to AC Volts Reg/Rec unplugged
Test between each set of stator wires at plug. 2000Rpm
-A to B = 15.2 give or take
-A to C = 14.8 - 15.2 give or take
-B to C = 15.2 - 15.4 give or take
Test w/ black lead to ground, red to each wire at plug
-A to B = .5
-A to C = .5
- B to C = .5
Multimeter to ohms.
Test between each stator wire at plug.
-A to B = 1.0
-A to C = 1.1
-B to C = 1.0
Test w/ red lead each wire at plug, black lead to engine casing
-A to ground = no measurement
-B to ground = no measurement
-C to ground = no measurement

Video uploading to youtube. when ready it will be here

04-18-2016, 11:10 AM
Based on the tests and research I think my stator is bad. Anyone else have to replace a stator on a Virago have any tips? Good place to buy from? Or even better have a stator? lol

04-18-2016, 11:17 AM
Your rotor/stator seems a little low, but is still balanced between the phases. I'd be much more suspect of the R/R.

04-18-2016, 3:25 PM
Your rotor/stator seems a little low, but is still balanced between the phases. I'd be much more suspect of the R/R.

Balanced yes, but shouldn't it be upwards of 50 AC Volts? not 15? That seems like it wouldn't be enough to charge a system to me.

I still have to test the reg/rec based on the simple test in the climbers. Theres not much you can do it seems….

My guess is when one goes it probably takes out the other so it will probably be a dual part replacement.

04-18-2016, 8:46 PM
You should be testing for amps coming straight off the alternator. Check your manual for expected results.
That being said 15 volts is more than your seeing after the reg/rect so try replacing it first.

Static check the reg/rect for any stray voltage leaking past the diodes back to the alt. If you see any it's toast for sure.

04-19-2016, 9:30 AM
I checked the reg/rec according to the test in my Clymers manual and it seems ok to me?
Multimeter set to diode
Black wire to ground, red to each of the three connections all have the little line symbol
Red wire to ground, black to each of the three connections all read 525-530
Black wire to reg/rec positive, red to each of the three connections all have the little line symbol
Red wire to reg/rec positive, black to each of the three connections all read 525-530

05-03-2016, 1:02 AM
I'm lost! Not sure what part(s) to order as the basic tests say things should be good....but then I still have low output in the charging system. I thought maybe removing the left side cover and checking wires/stator condition would help . . . .
This video is is a short clip showing the stator I just removed while looking for the charging issue. Was hoping to see some obvious damage so I knew if it was the cause. This didn't help me at all . . . except I know how to remove the stator now lol.
Any suggestions people? Stator looks ok, tests for ohm resistance ok, no ground faults.....reg/rec tests ok in regards to functioning diodes....but the output at the stator seems low to me and there seems to be no output from the reg/rec as the battery doesn't gain any increase in charge when at 3000rpm . . . I hate electrical! My assumption is a bad battery would not effect the output of the stator or Reg/Reg correct? Just the ability to charge/keep charge/ etc??
Would replacing the Reg/rec be the best first step in regards to the fact it's the cheapest of the two? If it's not the issue at least I have an extra.....I just don't want to shell out like $140+ to get a stator and find out its something else.
I also really want to be riding as it's all ready MAY!!!

(Video Link)

05-03-2016, 5:36 PM
Yes a bad batt will cause charging issues. Charge it and get it load tested.
Bad grounds and connections too.
A shorted stator. Weak rotor magnets even...
Stator output is measured in amps not really in volts AC

One: charge/test that batt.
Two: make sure the reg rect is grounded.
Three: make sure the stator is not grounded.
Four: Replace faulty components and/or repair poor connections/grounds

05-04-2016, 6:19 AM
here is the be-all-end-all of charging system troubleshooting:

3 pages of explanation, theory, and then the step by step tests to check everything.

05-07-2016, 6:50 PM
One of my instagram followers saw my post about the stator and happened to have the same bike. Ran the same tests I posted and compared numbers. My stator is a little lower than his but not much. Also happens to have an extra parts bike with a good Reg/Rec which I now think is the issue. Now that would all be pretty rad as is . . . BUT even more rad is he happens to be a guy who won a free sample of the beard care products I make around xmas. Then asked me if I would trade a few different scents in the beard oil and beard balm in exchange for the Reg.Rec . . . . so as of checking the mail next week sometime hopefully my issue is solved!
The internet is a funny place man!

05-18-2016, 2:49 AM
Quick update!
I replaced the Reg/Rec with the one the guy sent me. Re connected everything and fired it up. Output from the stator is still a little low so the end result is also a little low...BUT it's charging now! After idling, revving etc the battery tested .20v DC less than a fully charged battery...After sitting over night it was back up those .20v
SO I started tearing apart the ass end, removed lights etc and am currently deciding how much frame to chop before jabbing up some sort of fender situation and sissy bar. I also made some temporary hard tail struts out of some 1/2 x 1 1/2 flat steel the millwright at work gave me. Gonna test ride and see if I like it before committing to a frame chop/weld hard tail
Stay Tuned.