VFR400 - NC24,
I'm having some problems with the charging system - I have to keep charging the battery and this morning it cut out and wouldn't start on way to station - 6:15am - got the wife out with kids to bring jump leads so I could start of her car - managed to get it back home

I'll test tinight with my multimeter to see if it's charging properly and not overcharging and damaging the battery.

I've been reading that changing to the Yamaha R6 Reg/Rect is a better option, works a whole lot better than the std Honda one for this model

Is this correct and after looking on Ebay - is this model ok to use: YAMAHA R6 5EB MODEL 1998 - 2002

and

is it quite easy to change the connections to make it fit

Cheers

Yeha that one will work.

I use the 2003 - 2005 ones myself but apart from minor shape changes i'm not sure theres much difference.

Before spending your money though it is worth checking that this is problem.

Electrical Circuit works as follows.

Generator -> Regulator -> Battery

The genny produces all the power, this gets regulated down and runs the bike / charges the battery up.

To test the genny.

Unplugs the plug with the 3 yellow wires from your reg/rec.

Get a multimeter and set it to AC volts.. manual ones usually have 200 / 750 settings... 200 will be fine.

Connect Red lead to one yellow wire, black lead to another.. start bike and hold revs at 5000rpm.. you should have 50V.

Move the leads around so you have a different pair.. check all combinations.. should have 50V between all the phases.

If you do then for the moment it is safe to assume your generator is ok.

Reconnect the generator back up to the reg/rec and set your multimeter to DC Volts.. 20 setting if its manual will be fine.

Start and run the bike.

Measure the voltage across the battery terminals at idle with lights off.

Measure the voltage at battery terminals at 5000rpm with lights off

Measure the voltage at battery terminals at 5000rpm with lights on.

Best to replace the battery every 18 months to two years as well to protect your reg-rec.

As a battery gets old and subjected to harsh vibrations etc from bike it can't take good charge anymore.. the reg-rec has to burn the extra charge off as heat which cooks the reg-rec.

I find the Varta batterys from Tayna are cheap (approx £20) and good even after 2 years.. i just change as a precaution.

http://www.tayna.co.uk/YB9L-B-12N9-3B-P790.html

Get back to me with your voltages and we can go from there.

Thanks for the checks

I managed to do these tonight:

Connect Red lead to one yellow wire, black lead to another.. start bike and hold revs at 5000rpm.. you should have 50V. - I get 75V

Move the leads around so you have a different pair.. check all combinations.. should have 50V between all the phases.

If you do then for the moment it is safe to assume your generator is ok.

Reconnect the generator back up to the reg/rec and set your multimeter to DC Volts.. 20 setting if its manual will be fine.

Start and run the bike.

Measure the voltage across the battery terminals at idle with lights off. - 13.5v - 13.8v

Measure the voltage at battery terminals at 5000rpm with lights off - 12.8V

Measure the voltage at battery terminals at 5000rpm with lights on. - 12.7V

75V AC for the Genny outputs! and I thought the voltage would rise till about 15V at 5000rpm and peak there but it went down, so looks like when I'm out riding it isn't being charged,so with lots of short journeys the starting up the bike is draining until I need to recharge with battery charger.

I did notice something the other night, put lights on and they were quite dim but after a couple of minutes the headlight suddenly got brighter

When I had the bike serviced about 6/7 months ago they put in a new Reg/Rec, sourced from Honda.
It is mounted under the tank near the seat and has a large cooling fin - so I thought this would be good for a while

Cheers

I may be wrong (the VFR400 may be totally different from other bikes) but between 70vAC and 75vAC is a normal generator output per phase to me. It was on my FZRs and R6 and my old FZ track bike.

thunderace wrote:I may be wrong (the VFR400 may be totally different from other bikes) but between 70vAC and 75vAC is a normal generator output per phase to me. It was on my FZRs and R6 and my old FZ track bike.

Depends on RPM, at 5000RPM it should be 50v AC.

You'll probably get over a hundred volta at full rpm.

Genny souds a bit suspect, as do your battery voltages... (too low)

Should be 14.1 - 14.4v volts at idle / 13 - 14 at revs.

Your idle isn't too bad but when your running the bike it isn't charging the battery... I'd change the genny, battery and put and R6 reg/rec on to be safe.

You can pick all of the above up fairly cheap

David wrote: Measure the voltage across the battery terminals at idle with lights off. - 13.5v - 13.8v

Measure the voltage at battery terminals at 5000rpm with lights off - 12.8V

Measure the voltage at battery terminals at 5000rpm with lights on. - 12.7V

Those voltage measurements look suspicious to me. You should expect to see running voltages closer to the 13.5v that you got when it was idling.

Dodgy generator?

I'm sure someone will be along soon to confirm.

Cammo wrote:

David wrote: Measure the voltage across the battery terminals at idle with lights off. - 13.5v - 13.8v

Measure the voltage at battery terminals at 5000rpm with lights off - 12.8V

Measure the voltage at battery terminals at 5000rpm with lights on. - 12.7V

Those voltage measurements look suspicious to me. You should expect to see running voltages closer to the 13.5v that you got when it was idling.

Dodgy generator?

I'm sure someone will be along soon to confirm.

See post above :D

I agree with your findings!

Arrrg!!,

Was hoping not to have to change all 3 suspects.

When I had the Bike MOTd they checked all the charging system and that's why they replaced the Reg/Rec and some wiring.
The battery is no more than 18 Months old
I thought they had fixed this.

Thanks for all the advice.

I will clean connectors and re-measure - not sure why , just delaying the inevitable.
I can replace the battery and reg/rect - not sure about the genny

Do I need a special tool and is it a simple case of unbolt and rebolt and can I use a second hand one from Ebay?

Cheers

Very skint, so trying to get to the problem and hopefully not pay out too much.

I unplugged all connections related to the charging system, cleaned and reconnected - still no charge to battery.
Disconnected Reg/Rect from battery and measured output (red/green wires - nothing, well very very little and not stable)
So there is plenty AC going into Reg/Rect - 20V idle to 70/75 at 5000rpm but nothing on the output
Generator - Measured between yellow wires and got 0.5/0.6 ohms which I believe is correct and also checked between yellow wires and GND - there is no short there.

I was thinking of starting with the REG/REC first due to the results and also because it is a lot easier to replace than the Generator.

Does this sound like the way to proceed - any comments are much appreciated

Cheers

Genny is easy to replace...so stop being soft, get it fixed properly frst time and be glad you did it!!

You only need 1 tool - to pull the rotor off but this is no worries.

No need for papering over the cracks..