Light bulb blows with RPM

[NorthernRider]

I have a KTM EXC 125, my lights work, however, they're glowing brighter than they should, and whenever my RPM goes up / I rev my engine, they just blow out.

I asked around, and everyone told me its the regulator / rectifier, so I bought a new one, but my light bulbs still blow out.

(and no, its not the battery, EXC 125 doesnt have a battery.)

I really need help with this.
Thanks

[Nobby the Bastard]

Assuming you are putting the right voltage bulb in, if the reg/rec works then the sink for excess power is missing. If it isn't supposed to have a battery I'd be looking at the ballast resistor.
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[NorthernRider]

[stinkwheel]

If it's direct (A/C) lighting, you also need the correct wattage bulbs in.

Does it do it with the headlight fully on too or just with the daytime running/sidelights?
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[NorthernRider]

[Nobby the Bastard]

[NorthernRider]

[Pete.]

I had this on an old z200. It was the regulator/rectifier. Check the running voltage I bet it's up around 50-60v when it's revving.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Teflon-Mike]

First question; DO you actually have a licence to be able to ride this thing?

That particular bike, may be a 125, but it isn't A1 complient or Learner-Legal. I seem to recall its not even A2 complaint as the power-to weight ratio is too high and you cant 'restrict' one enough within the licence regs.

If you no have licence, and so shouln't be using the thing on Her-Magesties, then lights not working is probably not a problem. If you want to stay legal, park it up, stay off the road. If you dont care about the legality... well, a blown light bulb wont add much to the rap-sheet, will it? (Though may give them good cause to pull you in the first place.. but meh, you ride at risk, you take your chances!)


On to the actual blown bulb problem. This is a competition model build for off-road only use.... they only expect the lamps to be turned on at scrutineering, and they don't expect the scrutineers to be revving the buts off the motor during their inspection.... so again, WHY is this a 'Problem' (ubless you are trying to use it as an illegal L-Plate road bike, and dodge getting tugged!)

Non battery bikes, had/have a hobbit of doing this, blowing bulbs. In fact many battery bikes with more primitive electrical systems do too, but still.

In competition, the answer is you don't really need lights so just remove them. OR if as for competition Enduro, you loose points at scrutineering/check-points is the lamps dont wo4k... hopw manmy points might you use, and is it worth the faff for them extra points? I have known folk run no-lights MX bikes, and take the penalties for no-lights cos they are so small, for the faff of solving the 'problem', relatively. OR if they have to have working lamps, then they have gone total loss, and wired them to a push-bike lamp battery, for the small current they going to draw at scrutineering/chjeck-point....

Which brings us back to road use.... and is that even a great idea from the off?

Traditionally, in years past, on a road bike with a 'weak' electrical system, prone to blowing bulbs, the more usual answer was simply to pop a couple of spares, usually tail lamp and maybe a headlamp bulb, under the seat... "Sorry Orificer... it done it again.. hang on a second, and I'll fix itt.. swap in new bulb and ride off....

Faults usually were a knackered ballast resister or corroded ballast resistor terminals, or broken wire, and or the wrong wattage bulb.... and perversely many folk bunged in higher wattage bulbs than the book said in naive belief that they 'must' make more light.... or used 12v bulbs in 6v system, etc etc etc.

It's a KTM and a competition model, so I am some-whet sanguine at the suggestion "As STANDARD, the lights should work'.. they should and probably did.. in the show-room.... but its a KTM..... so who knows.....

Bulbs will blow because either a) they are old, b) they are cheap chitty bulbs c) they get too hot from too much current d) They get shaken excessively by vibration.... whats the odds on each possibility?

I would start by making sure that all the lamps were properly and securely attached, and any vibration damping in the mountings was actually there and able to work. I would look at the bulb wattages and the blb holders and clean all the contacts, and the switches and clean the contacts there too. THEN I would start looking upstream in ths system, and checking the alternator output... bulbs blowing when revved implies excess volts/amps, you dont have battery to damp, giving the regulator/ Zenner diode / Ballast resistor more work to do.. and then looking at that excess electric handling sub-system, like whether it SHOULD have a battery, and or the Regulkator/Zenner/Balast was shot or had coroded connectors or stessesed wires/connections....

But mostly, I would be wondering why I had bought a KTM, and all the reported problems that comes with one, like iffy electrics, especially on a competition model... and whether it was actually worth trying to de-bug....

Competition trick of going total loss, isolating charging and running lamps off a re-chargeable battery, would figure pretty high in my thunking.....

BTT do you actually have a licence to ride this thing in the first place?
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[Easy-X]

...and so endeth the sermon

So, back to the issue. I'm looking at the wiring diagram, yes... very odd not to have a battery for something I assume is used on the road. Engine cuts out in the dark and you're fucked! Anyhoo...

AC power comes from the stator and that drives the main lights directly. DC from the regulator drives the horn, indicators and digital dash (if you have that on your model.) The capacitor only smooths the DC circuit.

I would guess that either you're unlucky and your new reg/rec is faulty, you have the wrong reg/rec or the connection from the stator to the reg/rec is iffy, e.g. corroded connections. When you have this Mogwai issue (bright light! bright light!) do the indicators and horn work? If not then it'll be the reg/rec to stator connection. (A digital dash may or may not work, LCD ones need only a teeny-weeny amount of power to operate.)

If the indicators/horn are working then I'd take out the other bulbs connected to the AC side (main/back/numberplate/etc.) and jab a multimeter on the AC side and see what it you get at idle and at full revs.

To reiterate, the reg/rec is just that: it both regulates excess AC power and rectifies the AC to get DC.

If all else fails I suppose you could jab a meaty zener diode across the AC side to dump excess power.
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[stinkwheel]

[ThatDippyTwat]

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If the bulbs are getting too much voltage, how can it be anything but the regulator/rectifier?

What voltage are you getting at a wire going to a bulb, if you put a meter on the positive wire leading to a bulb and earth the negative probe?

Do these bikes always not have a battery? Could someone had bypassed the reg/rec?
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[jaffa90]

[1198]

[Kawasaki Jimbo]

[Easy-X]

[NorthernRider]

First off, I live in Norway, so the EXC 125 is registrated as an A1 over here (and yes, I do have my license)

Now, back to my issue.

I checked with a multimeter yesterday, using both the new regulator and the old one.
The old one was giving around 3-6V, which is waaay too low. (it should be around 12v)

Now the new one however, it's not doing its job AT ALL. It was giving around 20v, and 30-40v if i revved the engine. I think I might have gotten a faulty regulator from the dealer, but i'm not completely sure.

[NorthernRider]

[NorthernRider]

[Nobby the Bastard]

[stinkwheel]

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[NorthernRider]

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