Lower idle when lights are on

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TheJackRabbit
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Lower idle when lights are on

Post by TheJackRabbit »

I have a 97' 220 and when I turn the lights on the idle lowers. if i don't have the idle turned up then sometimes the bike will stop running with the lights on, but with the lights off it idles just fine. It's not a huge problem but could this be an early sign that the coils are going bad?

the bike has always done this since I got it 6 months ago

I've never had the flywheel off to look at the coils

is this what is supposed to happen? does anyone else have a bike that does this?
http://www.youtube.com/allthatstuff35 <--- some KDX videos here
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bufftester
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Re: Lower idle when lights are on

Post by bufftester »

I have never had that issue with my '01 220. The lighting and ignition circuits are for all intents and purposes isolated from each other, though they do share grounds. The coils are inductive and produce no load on the motor (in fact the lighting coil is always producing current even with the switch off). I would check all the grounds first, there are a couple of them at the ignition coil (just round spade terminals under the mount bolts) and it is possible that some floating voltage there could affect the ignition coil. Make sure they are clean and free of corrosion and secure, also make sure that all your connectors are clean and connected firmly. They have a tendency to collect gunk and usually don't get a lot of attention, so a good spray with contact cleaner would be good. There has always been speculation that rewiring the lighting coil improved spark somehow, though likely that is just perceived.
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TheJackRabbit
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Re: Lower idle when lights are on

Post by TheJackRabbit »

I'll dig into my big tomorrow and clean all the connections and grounds

I have herd of the KDX's leaking in the crank case allowing gas to get on the stator and ignition coil, if they were wet either from that or from water getting in there from washing, would it cause a similar scenario?
http://www.youtube.com/allthatstuff35 <--- some KDX videos here
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bufftester
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Re: Lower idle when lights are on

Post by bufftester »

Doubtful, the stock coils are sealed and the wire is enameled to prevent that sort of thing. Normally if it got wet and there was a break in the sealant it would short and just not work at all. Can't hurt to take a look and just make sure all the grounds are tight as well as the coil mount screws, it doesn't take long if you have a flywheel tool, but if it's running though then the coils are working fine and I wouldn't bother with the hassle of pulling the cover off.
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Re: Lower idle when lights are on

Post by KDXnoob1 »

With my basic understanding of eletrical I would imagine nothing is going bad. Mine does it too. I would assume that when you turn on the lights, it is probably places a larger draw on the stator and provides a slightly weaker spark to your plug. Allowing for further incomplete combustion and it seems to idle lower as the combustion isnt as strong.
But hey, I could be wrong. I'm in school for diesel so I'm probably so far off.
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bufftester
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Re: Lower idle when lights are on

Post by bufftester »

That would be exactly right if the system used just one coil to drive everything, but the KDX has separate coils for ignition and lighting. More likely is a ground loop issue since the CDI and the lighting circuit (w/regulator) share the same ground plane. It's possible this is just normal for the KDX and it's wiring and that I've never noticed it since I rarely rode with lights on. I'd try it now but my lights are currently not wired on the hybrid and I'm lazy :grin:
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Re: Lower idle when lights are on

Post by cragwl »

Yeah, when I would turn on my lights, I used to notice a idle difference. I now have a Steahly lighting coil and the idle stays consistent. I did however clean up the ground contacts too. Hmm.. I guess I'm once again, no help.
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Dekon
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Lower idle when lights are on

Post by Dekon »

I'm no electrical engineer, but isn't the idle issue caused by the increase in load on the lighting stator. Kind of like when you are using a generator and increase the load on it, it bogs for a second and then runs as usual. Just throwing this out there.
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Re: Lower idle when lights are on

Post by 559stan »

Even a car slows its idle when a eletrical load is introduced. Now cars have efi so you don't notice the idle step servo opening the throttle body. My 93kdx slows the idle when i turn the lights on. Sounds like a pilot jet issue.
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rbates9
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Re: Lower idle when lights are on

Post by rbates9 »

bufftester wrote: The coils are inductive and produce no load on the motor
:hmm: So, the lights are free power? I was under the impression that energy can not be made with out using energy... :pop:
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TheJackRabbit
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Re: Lower idle when lights are on

Post by TheJackRabbit »

I just cleaned out all the wires that go to the cdi and regulator, the blue wire that comes from the cdi to the ignition coil was especially packed with dirt.
I'll have to see how it runs tomorrow

thanks for all the input thus far
http://www.youtube.com/allthatstuff35 <--- some KDX videos here
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bufftester
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Re: Lower idle when lights are on

Post by bufftester »

The lights are not free power. The engine is spinning the flywheel, which has a large magnet attached. As the magnet passes across the ignition primary coil (or the lighting coil) the magnetic field is coupled and then collapsed, causing a voltage spike. The energy is not free, it is being converted from the combination of the centrifugal force of the spinning flywheel and the changing magnetic field between the magnet and coil. It's why you can bumpstart your bike with out a battery. In that instance, instead of burning fossil fuel to spin the flywheel you are using the kinetic energy of the bike to spin the flywheel. The result is that some of that energy is then converted from centrifugal force/expanding-collapsing magnetic field into an ac current. The difference in a car electrical system is the alternator is creating the sole voltage source, so of course any additional load, regardless of whether its lights or radio or whatever, is going to be evidenced in the whole system. It's also the reason that your bikes lights are brighter at higher rpm, because there is greater centrifugal force in the flywheel spinning at higher speeds. The regulator is supposed to limit the voltage to a set level, but there is some "slop" in the system and that's why your lights waver. For most people it is just easier to think of the flywheel magnet and the coil on the stator plate as an alternator, as it basically does the same thing.
When you rewind the lighting coil, you do it with a larger diameter wire. This results in a higher current being induced into the coil by the spinning magnet, and a smaller (slightly) voltage because the number of turns has decreased.The voltage induced in the coil is proportional to the number of turns in that coil, the flux density of the magnetic field (which is dependent on the magnets physical properties), and how rapidly the magnetic field passes through the coil (RPM). Higher current=more work, so you can now run lights with bigger wattage (work demands). The fact that the voltage has decreased is insignificant except at very low rpms. Now it is possible that a secondary magnetic flux field interacts between the ignition coil and the lighting coil because of their proximity on the stator plate, and the fact that the stator plate itself can interact with both coils and the magnetic field. And it would probably make a great thesis project for a budding engineer. But since I already did mine I'll leave it to someone else. The whole point of separating ignition and lighting is precisely so changes in one don't affect the other. With that said, as I mentioned earlier, the ignition side of the house and the lighting side are tied together through the ground plane, and so any anomalies there could cause an effect in either one, and is why you should make sure your connections are clean, corrosion free, and secure. It's also one reason why in the Baja Designs kit (and other aftermarket lighting stator kits) the lighting circuit is isolated from frame ground and instead works on a floating ground, providing more isolation between both sides of the circuit. Anyways, my fingers hurt from typing. It's a simplistic explanation, but then I work on airplanes so what do you expect :lol: oh, and btw I am an electrical engineer...really wish I was a rocket scientist instead :prayer:
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rbates9
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Lower idle when lights are on

Post by rbates9 »

So where do you get this kinetic energy? I looked at the parts store and the bike shop and neither one had any in stock. I just wanted to see if I could get right away from the fossil fuels and just go with the kinetic energy to keep the crank turning.


P.S. I was just messing with you about the free energy. :grin:
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TheJackRabbit
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Re: Lower idle when lights are on

Post by TheJackRabbit »

After cleaning all the connection and grounds, both under the tank and the seat, the flicker seems to be reduced from what I can tell in the daylight, and the idle doesn't dip quite as much, just slightly like 60 rpms worth probably

the wire that was most concerning was the blue wire that runs to the ignition coil with the different style connector, it was the most dirty of them all.
so even if cleaning the wires did nothing to performance at least I have the peace of mind that they are all clean now

BTW I was running a 10W rear bulb awhile ago, not since this thread started and with that in compared to an LED bulb the front light didn't flicker as much at idle
http://www.youtube.com/allthatstuff35 <--- some KDX videos here
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