Hi,

Need your help please!
I have a honda cbr 1987 1000cc engine in my locost.

It has a new battery in it at full charge at the start of the journey.

The alternator was charging at the start of the journey at about 13 volts.

Went out last night and all was great but about 20 mins into the journey the car started spluttering and dies

Voltage had dropped below to about 11.5 with out ignition and 11 with ignition on. it wouldn't start at all.

When we did get it started would run for about 5 mins or less then die again.

It seems when lights are on and the fan it can't handle it at all. When driven with fan on alone the voltage seems fine and runs well.

Any suggestions on what to do?



Cheers

Oli

Ne alternator or alternator overhaul.
The alternator is producing some voltage It is not charging 13v isn't enough to charge a battery you need at least 13.4v with the headlights on more if you have a battery with enhanced chemistry. Most cars built within the last decade charge at 14.4 v some close to 14.9v


Before fitting a new battery always charge it and then do either a cranking voltage test or it tested on a high load volts drop tester.

If you measured 13V at the battery, that's no proof that the generator was giving you a charge. You might expect to see about 15V across the battery after starting as the generator replaces the charge taken in starting.
Does the red battery light behave as normal ? ie is it on when you turn the key and go out when the engine starts running ?

The regulator units can be weak on these bike engines I have heard of lots of them failing and people tend to fit a fan and heat sink when used in a car to prevent them from overheating.Maybe the regulator has just failed.
Paul

I would suggest you need more amps, as when you connect everything the voltage drops.

You need to ensure your alternator is operating correctly or get a new one. One with more output will help

quote:

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Originally posted by big-vee-twin
I would suggest you need more amps, as when you connect everything the voltage drops.

You need to ensure your alternator is operating correctly or get a new one. One with more output will help

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Assuming you have a Lead acid battery,disconnect alternator from battery and measure alternator voltage off-load =>14.4V max 15.something.Otherwise regulator is knackered.

[Edited on 12/11/12 by Fatgadget]

quote:

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Originally posted by Fatgadget
Assuming you have a Lead acid battery,disconnect alternator from battery and measure alternator voltage off-load =>14.4V max 15.something.Otherwise regulator is knackered.

[Edited on 12/11/12 by Fatgadget]

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I thought it was a bad idea to run an alternator without a battery across it?

I,ve had a couple of regulators go down he Honda ones are weak.

Unplug and you will have three yellow wires coming from the engine, measure the resistance across pairs of wires and they should all be equal this shows that the windings are okay.

Look on eBay for a regulator from a 12v bike above maybe 250cc that has a decent heat sink on it and swap with what you have, no point in spending loads because it has Honda stamped on the side, the one on my fireblade engine came off a Ducati and cost £10.

Pretty much all bikes work in the same way at this level of electrics.

Another thing to look for is poor joints, a lot will have melted plugs as they age and the plug connections brake down.

NB/ when connecting the yellow wires can be in any order.

Regards Mark

Found this looks like a great guide!!

http://www.thegsresources.com/garage/gs_statorfault.htm


Oli