Just thought I'd try here, have a cut and customers 86 XV 700. Been rewired using an original wiring loom, new rectifier, battery is good also, when I charge it is fine and will work ok that day. Leave it a few nights and the power is reduced considerably and like all XV's takes a few turn overs when cold and the battery dies..... Any ideas.

Also want to fit a neutral light how do I do that one.... Not so simple

Any help from the tech heads much appreciated

Does it have an alarm fitted? Then could be a source of the power drain coupled with the cold temps at night. Is the battery new? It may charge up ok but and old battery might not hold the charge being put into it from the generator. I am no mechanic but these are things I would be looking into if it were me, starting with a new battery.

Best of luck.........66

It's been doing this for as long as I've had it, new battery made no difference, it over heated the rectifier so I replaced it, the battery when detached and charged fully retains the charge it will start my other two bikes of almost twice the cc as the old yam, I've looked at the easy fixes..... But maybe there is a auto electrician out there who knows.....I actually went to an auto electrician in Dundee he wouldn't go near it said because it wasn't standard....I said are you an auto electrician or an auto fitter?..... He didn't really know what to say.....good mechanics and auto electricians are hard to find in this modern age of fitters calling themselves mechanics

I don't know how it worked in the marines johnny but when i joined the RAF i started as an aircraft mechanic. it was 3 years on job training and a 6 month course before i was promoted to a fitter.                                                                                                                                                                              

time for new battery, cells will be knackered. simple quick fix                                                                                                                                                                             

it also sounds like its not charging, diode in gen blown ? check output from it first. get a cheap muiltimeter.                                                                                                                                                                              

  Re Danny's last post .... that was my 1st thought   Johnny, have you checked the generator output ?   I suspect your problem lies there   Particularly as you've mentioned that it has already overheated the rectifier   I'd be "investigating" the generator   A duff generator will kill a battery too   But if the battery does hold a charge and works on another bike without failing, it's unlikely to be that components fault   Stick at it Johnny and let us know how you get on                                                                                                                                                                               

think on this age of bike magneto we're not great                                                                                                                                                                             

  True Danny, but they certainly didn't kill batteries or rectifiers when they were new   So despite it's age I don't think the power "rating" is the issue   More likely to be a dodgy generator   I'd also suggest checking ALL power & EARTH connections   A BAD earth is the most likely culprit of flattening the battery                                                                                                                                                                               

Generating fine had the meter on it, tested at around 3000rpm.....holds for about a day maybe two, almost as if it's draining somewhere but can't figure out what or where...the rectifier has been fine for the last year and a half ......

Is there not a unit somewhere I recall that allows charge in but prevents escape, I forget the technical term....

Re fitter.....don't take it personally but there is a difference between someone that can fix something that is damaged through mending and replacing a part..... I know a few mechanics old school who mend re work a part rather than just replace parts until it works like in garages these days....

and I spent a few years training the fleet air arm when they were going to afghan, some of the aircraft mechanics could get around an engine on anything, strip, mend fix others didn't have a clue and would go through the 'procedures'.....it's the individual capability not the job spec....some are better than others... If you are of the better, my apologies if not well...that's life I'm afraid...

Anyway I'll get to the bottom of it, try cleaning all connections and earths see what happens...

  Johnny, what you might be refering to is a Zenner diode   It's not strictly a "one way" electrical "valve" but it will only allow current to flow in the reverse direction when a certain voltage is reached (typically 0.7 V)   They are usually built into modern (post 70's) reg/rectifiers   The regulator regulates the overall voltage   The rectifier turns AC current into DC current which is powering the bike's electrics   The zenner diode is supposed to shunt excess current to earth to prevent frying the electrics ( as far as I know  )   But we may have some electrical boffin on here who could verify that ?   Anyway I suspect that "may" be where there is a problem even if it has been OK for 18 months   Components can faill suddenly without warning, substituting that component with another known good one may well fix the problem   But unless & until you find the cause of the failure, it's almost certain to suffer the fate of it's predecessor   But is the voltage output "stable" at above & below 3000 RPM ?   Like I said, I'm not a qualified auto electrician so all this is just pure speculation   Checking ALL connections particularly the earths will certanly eliminate that particular issue of an earth "drain" which IS the most likely cause IMHO                                                                                                                                                                               

  As for the neutral light switch   Is there still a switch installed in the gearbox ?   If so its a simple matter of acquiring a suitable lamp holder with a green lens (readily available in auto spares shops & on ebay)   Taking a power wire to the bulb & running a wire to the earth side of the lamp holder from the switch on the gearbox   If there's no switch in the gearbox you're on a losing streak   When I started out we didn't have such "refinements"   We had to find neutral "manually" (or at least by foot LOL)   When they 1st appeared we called them "idiot" lights   These days they are usually referred to as "tell tales"                                                                                                                                                                                 

The neutral light the mot tester said I needed on, I got around the indicator thing as the front indicators have lenses on the back to see when there on, I know there was on on the original bikes so I'll try to find the wiring point. Thanks for the advice so far I am a lot further on now than before

hi there johnny.... to find if there is a drain on the system disconnect the positive terminal on the battery then connect a test meter or test light between the positive terminal and the cable end... if it registers a voltage or lights up then there is a drain and simply disconnect components untill the voltage drops to zero or the light goes out usually go for the reg/rec first then cdi if fitted (dunno what engine it is ) also depends on generator wether its a self exciting type or non self exciting type... the self exciting type has its own magnets to create a generating field but the non type takes a feed from the common live in the loom when the ignition is on to power up a couple of extra coils in the generator to create the magnetic felds it needs..have known batteries to leak down this path as well....hope this helps a bit......                                                                                                                                                                             

As far as i can remember the neutral lamp isnt required for an MOT, especialy on the the age bike your talking about.

If the bike never has this fitted from the factory then the MOT tester can not apply new regs retrospectivly. Maybe try a station where hey know whats what or make a quick call to the ministry of tansport inspectrate to make sure. In fact on a bike of hat vintage if its not fitted i cant be tested, if it cant be tested it cant fail. Head lamps and indicators are the same, if they dont work remove them and blank the switch. Only exemption is brake light ,horn and speedo.

Cheers guys,

I'll try those battery tests. It did have a. Neutral light and indicator lights before I cut it down took the whole top end of replaced it with hand made bars hand a small digital speedo... But yeah I was surprised when the tester said about neutral light and indicator turn dash lights and I'm not even going down the route of the old fashioned black and silver number plate lol, I know that's illegal but no one seems to mind lol

i did have similair probs with a worn faulty ignition barrel, changed it all well. (batt only lasted a day or 2).                                                                                                                                                                             

It's not The ministry of transport inspectorate now it's VOSA and I cant see any reason why you would need a neutral light for an MOT as for indicators I think any bike built after 2004 must have them unless they were NOT fitted as standard IE trials bikes that had lights but not indicators

It's not a standard bike been cut and customised but it did have on originally, it was an xv 700 virago                                                                                                                                                                             

Blank off the switches and remove bulbs etc, then it cant be tetsted.