honda vfr400 nc21 dead battery

badboy1974 · Derestricted Danger Joined: 24 Mar 2005 Karma :

hi guys,
i am in urgent need of advice, i have replaced my regulator rectifier with a secondhand part, but the battery is still going flat...the guy i bought the bike from says he replaced the battery any ideas...anyone?? :( :(

pirate · L Plate Warrior Joined: 14 Feb 2006 Karma :

I think your best bet is to buy a new regulator rectifier .
Had the same problem with an nc30 it cost 120 euro for the regulator rectifier or drop it into ur local dealer,they find the prob quick enough and wont cost a lot for them to check

www.125power.com · Crazy Courier Joined: 04 Jan 2006 Karma :

Run a voltage meter across the battery terminal with the battery fully charged and fitted to bike. Starting bike should see the volts dip then rise again and maybe rise to 1-2 volts more than battery with engine dead, revving the bike up should see an increase in volts too also you will probs notice the headlight brightens as you rev bike, if this is not happening buy a new regulator or have old one tested
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badboy1974 · Derestricted Danger Joined: 24 Mar 2005 Karma :

cheers guys ill take your comments under advisement..
Very Happy

does anyone have workshop manual in pdf format for nc21??

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

First job load test the battery but unless you have a load tester you won't be able to. They coast about £45 from machine mart.

Start your bike with the lights off and connect a multimeter set to DC across the battery. You should get a reading of around 14.2 volts at idle rising to around 14.9v max when reving.

Try the same with the lights on and tell us your reading.

Next dissconnect the generator and start the bike. The generator should have 3 yellow wires coming out of it. Now connect a multimeter set to AC to two of the wires in turn so you do a total of 3 tests. Rev the bike and you should get a reading of around 50-60Volts.

If on any test you don't get a decent reading theres your problem.

badboy1974 · Derestricted Danger Joined: 24 Mar 2005 Karma :

thanks again guys...have tested voltage from battery, and from alternator...the reading from the alt was less than shit...so i have got one coming, will relace and re-check voltage output..
cheers again Laughing