Nsr 125r 51 plate charging probs

[Erect Bal Bal]

Hi there i am hoping someone can help me.I am 35 years old and not new to bikes but this has got me stumped.I have just brought a 51 plate nsr125r to run to and thro work as i dont want to put to many miles on my RD500.The nsr wont hold a charge the battery was flat so i got a new one.This was fine for 2 days but then the bike started to cut out on low revs and i just got it home.Put my volt meter on the battery with the bike running and it was showing just over 13 volts but the moment i rev it it drops down to 7 vollts so it is doing the reverse of what it should do.Found the regulator rectifier and it was hot.Got a second hand one from e-bay which came to day fitted it and it still does the same.So could some one please point me in the right direction.Many Thanks

[alains]

you need to check your alternator stator . prior dismantling it check continuity in the wiring . exiting the stator you have 3 yellow wires and a black/red (dont care about the 2 small wires coming from the impulses coil) . these 3 yellow are plugged on the rec/reg , unplug them and check continuity between one and the 2 others (you should find 0.7-0.8 Ohm at each mesurement) . then check continuity from one yellow to the green and it should be no continuity . in case one of this mesurement is wrong , you must replace alternator stator . note that the black/red wire is for the CDI charging (~200Volts AC at 4500 rpm) .
a short question : what do you mean when you say "on a 51 plate" , the only way to tell the year is on the serial number between the yokes and a specific caracter
exemple ZDCJC22C0YFxxxxxx the Y shows 2000 bike
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the worst day fishing is better than the best day working

[Erect Bal Bal]

I have done the checks that you have said and every thing is fine the number on the serial is 01.Please help as i am at a total loss.

[Trixie]

Any "extras" fitted onto the bike such as a different headlamp, indicators, horn, etc? Dodgy alarm? Any of this could be putting unneccesary strain on your battery/charging system.
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Dead nobodies in company cars...

[alains]

ok . now unplug the wires on to positive of the battery . put it in charge with an outside charger during 6-8 hours at low intensity (0,5 to 1 Ampère) when finish , unplug charger , check voltage and if it's less than 12.9 Volts change battery . if ok , let it for 2-3 hours then check voltage again and if you've lost 0,2Volts or more change your battery
i will explain : 12V batteries ares composed by 6 plates covered with stuff , as new each element is 2.2Volts end of charging ,1.9 Volts end of discharging (13,2 & 11,4 volts) and the capacity is proportional at the stuff . with age & use the stuff goes off the plates so the capacity will fall down and the voltage as well , and we say "battery doenot keep charge" , this is why it's important to make 2 mesurements spaced at least 2 hours and see if the voltage get lower
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the worst day fishing is better than the best day working

[Erect Bal Bal]

I have fitted a brand new battery and have put it on my optermiser for 48hrs there looks like there was a alarm fitted at some time of its life a datatag one and some won has cut it out so i am going to get a new loom from e-bay and change it then see what happens

[Erect Bal Bal]

Now it has lost its bloody spark.Just like me is the cdi the cause please help.Or if any wants to buy it thay are more than welcome to make me a good offer.

[Erect Bal Bal]

The bike has only done 3995 miles recorded it ran fine untill today.Just had a full respray in black and has been put into west stickers new battery and new front wheel bearings good looking bike i live in kent.But if i can fix it i will keep it

[Smiffy1203]

not sure if they have fuses but check them if they have, my mate had the exact same problem on his Evo 5 turned out to be the battery fuse after changing the battery and alternator(what a ball ache job on them!!)

[Erect Bal Bal]

There is one fuse that i can find and it comes off the battery and it is fine.

[Smiffy1203]

maybe a bad earth (not sure how to check this on a bike lol) or check all the leads are attached to the alternator and no wired are corroded maybe spray a little WD40 on the alternator

[johns]

may be the batter is flat and need a new one as it got any water in it

[Erect Bal Bal]

It has got a new battery on it and it is full of acid it charges up to 13.4 on my charger let it stand and it shows 12.9. Two hours later it shows 12.7 this is the reading i get when the battery is not on the bike

[alains]

may be you've got something draining the battery , unplug the positive and by scraping the terminal on the pole look if it makes sparks or insert an amperemeter between the terminal and the pole
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the worst day fishing is better than the best day working

[Smiffy1203]

if the battery aint on the bike but its losing power then i would say u bought a duff 1 it could be one of the cells is down in the battery, it would be better to find some1 with a working battery and swap it over see what happens.

[johns]

what charges is it a bike one or car one

[alains]

best is 0,5 amps during 8 hours
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the worst day fishing is better than the best day working

[johns]

were did you get the battery from

[Erect Bal Bal]

My local motorbike shop brand new.