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Old 06-01-09, 01:50 PM   #11
svdemon
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Default Re: Why do my lights get brighter when I rev the engine?

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It's not a good thing. the regulator does exactly that, regulates the voltage. If your lights get brighter with the throttle then it's on its way out and will probably take the battery with it.
Is this right? Mine does this when its cold certainly.
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Old 06-01-09, 01:51 PM   #12
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Default Re: Why do my lights get brighter when I rev the engine?

I know older bikes with dinamos do it but the regulater should stop it from doing that. Do you blow bulbs a lot?
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Old 06-01-09, 01:53 PM   #13
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Default Re: Why do my lights get brighter when I rev the engine?

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It's not a good thing. the regulator does exactly that, regulates the voltage. If your lights get brighter with the throttle then it's on its way out and will probably take the battery with it.
The regulator provides a "stable" voltage, but what does it do for current?

The brightness of a bulb is determined by the power (watts). This is voltage x current.

If the voltage remains constant, but the current is increased, the bulbs will get brighter.

NB, My lights get brighter when the engine is revving compared to idling. Also, when I honk the horn, my lights get dimmer, regardless of the revs. That is current changing in various parts of the bike, not voltage. Note also that my horn is far from stock, drawing around 50amps.
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Old 06-01-09, 02:00 PM   #14
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Default Re: Why do my lights get brighter when I rev the engine?

Mine is a pointy, never blown a bulb and never had any trouble with it. I have got Osram nightbreakers in it if that makes any odds.
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Old 06-01-09, 02:02 PM   #15
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Default Re: Why do my lights get brighter when I rev the engine?

could be just one of those things but I know if it was mine I'd check it over with a multimeter and just make sure its o.k.
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Old 06-01-09, 02:02 PM   #16
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Default Re: Why do my lights get brighter when I rev the engine?

Current is the voltage divided by the resistance of the system. It's not a tap. Given that reving doesn't reduce the load on the electrical system, then it must be due to an extra voltage being produced by the alternator. I guess the rectifier should be sorting that!
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Old 06-01-09, 02:03 PM   #17
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Default Re: Why do my lights get brighter when I rev the engine?

Help arrives just in time!
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Old 06-01-09, 02:20 PM   #18
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Default Re: Why do my lights get brighter when I rev the engine?

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Current is the voltage divided by the resistance of the system. It's not a tap. Given that reving doesn't reduce the load on the electrical system, then it must be due to an extra voltage being produced by the alternator. I guess the rectifier should be sorting that!
Current is actually a flow rate. Nothing more. Think about tidal currents etc. There's a reason they share the same descriptive name. With a tidal current, you have the same volume of water, moving at a different vector (direction and/or speed).

When the engine rev's higher, the alternator puts out a higher voltage, at a higher flow (current).

The regulator then ensures that this increased voltage is reduced to 12v (approx). The current generally isn't reduced by the regulator.

By upgrading bulbs (eg, Osram Nightbreakers as stated), the bulbs are designed to glow brighter. This is accomplished by drawing more current due to lowered resistance in the coil. If the alternator isn't putting out maximum current (for the bulbs) they will be dimmer than they can potentially be. When the current raises (by revving the engine), naturally the bulbs get brighter.

In my case, when I honk the horn, some of that flow (current) is diverted away from the bulbs to the horns. Thus making my bulbs dim. I also have uprated bulbs FWIW.

Further to this, my bulbs get brighter when I rev the engine (I'm talking only the first few thousand RPM, then it's constant). I have tested the rectifier, and alternator. Both are fine the last time I tested them (after approx a year running with this setup).
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Old 06-01-09, 02:31 PM   #19
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Default Re: Why do my lights get brighter when I rev the engine?

It may be worth noting that a regulator keeps voltage within acceptable limits, it doesn't keep it at a constant value. More revs will produce more voltage than a low idle will, everything gets a bit brighter, and the regulator stops it getting too silly. 14-and-a-bit volts is quite a common reading at ~2-3,000 rpm, you're likely to be a bit lower at idle.

Frankly I wouldn't worry unless there are other symptoms, or the bulbs are going from seriously dull to blinding, and keep getting brighter the higher you rev.

FWIW, I think Lozzo's diagnosis has got some substance to it. Do that

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Old 06-01-09, 02:37 PM   #20
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Default Re: Why do my lights get brighter when I rev the engine?

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It may be worth noting that a regulator keeps voltage within acceptable limits, it doesn't keep it at a constant value.
Exactly why I chose my wording carefully. But I agree, it's a point worth clarifying.
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