Weird voltage issue.

[Kram]

just checked over my bike to try and find out why it misses...

and got to the electrics, on idle (and all through the rev range) with lights off, the battery is about 14.4V. when i put side lights on, it's slightly less.

When i put full beam on the voltage goes down to about 13.3V and down to about 12.9V, and at this point the bike stops off idle(though it's very lumpy).

Also the bike cuts one cylinder at 6k revs when the lights are on as well.

it has had a new battery and Reg/Rec about 2 months ago.

can anyone shed some light on this?

thanks. Drummer
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FS1E -> SR125 -> CB400N -> CB650 -> FZR600 Genises -> VFR400 NC21 -> CBR900RR Fireblade -> Renault Clio 1.4

[the grim reaper]

You say that the battery voltage is about 14.4V at idle? That sounds high to me. What does the voltage go to when you rev it? If it's above 14.5V it's cooking the battery, that could be a reg/rec problem or an alternator problem.

If it doesn't, my guess is that you have more than one problem. If it cuts only one cylinder at 6k, I'd say spark plug/HT lead, if it actually cuts two, I'd say coil.

The idle voltages with lights on etc are fine, as long as the battery is above 12V then the relays will switch OK. I'd say that the idle problem is possibly down to the coil drawing more current than it should, difficult to say.

I'd replace the spark plugs as a check as it's cheap and easy to do. Then I'd start looking at the coils and HT leads.

Cheers

Grim
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Adverts don't always work: Remember that advert, where the army are running across the desert and they have a wounded man on a stretcher. They get to a ravine, the bridge is down and a caption pops up that says, 'What are you thinking?'. I don't know about you but I was thinking, 'Christ, I'm glad I'm not in the f***ing army'.

[Kram]

the voltage on the battery at idle (idle of 1.4k) is about 14.3-4 but i can red line it and it still says 14.4V doesn't move a notch.

i replaced the plugs a few months ago, i will look at them when i get some free time.

it's a real nuisance as i can't get into the powerband to overtake so easily
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FS1E -> SR125 -> CB400N -> CB650 -> FZR600 Genises -> VFR400 NC21 -> CBR900RR Fireblade -> Renault Clio 1.4

[the grim reaper]

I could give you a hand if you fancy a ride to the New Forest at any point. Send me a PM if so, I'm a leccy Engineer by trade so I should be able to help

Cheers

Grim
____________________
Adverts don't always work: Remember that advert, where the army are running across the desert and they have a wounded man on a stretcher. They get to a ravine, the bridge is down and a caption pops up that says, 'What are you thinking?'. I don't know about you but I was thinking, 'Christ, I'm glad I'm not in the f***ing army'.

[Kram]

gimme ur postcode, and i'll come up when i have a free day.

monday any good???

i'll buy some new spark plugs as well
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FS1E -> SR125 -> CB400N -> CB650 -> FZR600 Genises -> VFR400 NC21 -> CBR900RR Fireblade -> Renault Clio 1.4