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My gts250 has a headlight modulator. At idle the headlight modulates fine . When I drive it or rev it on the center stand ,the headlight will stop modulating and then go dark and then flash very slowly. I took off modulator and the headlight is fine when I rev it. My question, is it the modulator or could it be the voltage regulator or something else. The company that produced this has not seen a symptom like this before.
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09 GTS (sold) 2014 NC700XD
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UTC quote
It could be the voltage regulator. Check the voltage across the battery, it should not be above 13.7 volts with the engine revved.

For interests sake, who manufactured the modulator? I had problems with mine when I bought it, but they have been sorted.
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2007 GTS
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2007 GTS
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UTC quote
with the modulator removed and it acts fine then its the modulator. but like it was suggested do an electrical volt test.
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UTC quote
Midnight Rider wrote:
It could be the voltage regulator. Check the voltage across the battery, it should not be above 13.7 volts with the engine revved.
If the battery is already fully charged it can go to 14.6V quite happily. Above 15V and the regulator is toast.
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UTC quote
I learn something new every day. Thanks for clearing that up!
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UTC quote
Kriss industries.
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UTC quote
I will check the voltage.
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UTC quote
Checked the voltage at 3000 to 5000 rpm and it read 14.40 volts , so it must be the headlight modulator. The battery was at full charge when I tested. Thanks for the help.
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UTC quote
I have no knowledge about Kriss, I know the company I bought mine from said the electrical circuit was extremely noisy and they needed to adjust the hardware some to make it work properly on the Vespa they had in to test it on. It's been flawless ever since
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UTC quote
If it is noise on the 12V line then a 100µF and a 0.1µF in parallel across the 12V as close as possible to the modulator might do the trick.
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UTC quote
Jimc how would I go about doing that? What is a 100u ? I have the same modulator on my lx190 for 4.5 years and it is fine. I'm pretty sure the modulator was working ok on the GTS for 14 months prior.
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UTC quote
valval wrote:
Jimc how would I go about doing that? What is a 100u ?
They are capacitors - the 100µF is electrolytic (polarity sensitive). Fry's or Radio Shack should have them in stock. Just solder across the 12V line into the modulator. Don't forget the 0.1µF one, it's probably the more important for spikes on the line.
Quote:
I have the same modulator on my lx190 for 4.5 years and it is fine. I'm pretty sure the modulator was working ok on the GTS for 14 months prior.
In which case either the modulator has developed a fault, or your bike has become more electrically noisy. Check your spark plug is firm attached to the cap, and the cap to the HT lead.

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