New to motorized bikes, 13 years old, CDI's always burning out?

JoelMiller

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Jul 12, 2021
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Hello, I am new to building motorized bikes, and I am 13 years old. I’ve built the bike by myself and it worked wonders, propelling me at 30mph.

My CDI boxes I buy almost always turn out junk right out of the box and if not they burn out within a few minutes. I made sure I bought the supercharged CDI since on here it seemed to work pretty good. I ran diagnostics with my Ohm meter to make sure it worked but only a piece of the CDI assembly works. Any suggestions fellas?
 
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Chop-chop

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May 19, 2021
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That's the point an inline switch just cuts the circuit instead of shorting it out leading to or contributing to failure.
Please learn about fundamental electricals before engaging in this discussion any further. Please.

The reason the factory has a kill switch that shorts the system to shut it down instead of one that cuts off the current is BECAUSE you do not need the current to run to the switch and then to the coil etc the entire time when the engine is running. What I'm saying is, they designed it like that so that the kill-switch circuit stays neutral with no current running thru it whilst the engine is running hence LESS CHANCE FOR SOMETHING (THAT IS UNNECESSARY) TO GO WRONG. Also your suggestion of running an Inline switch also adds extra resistance to the circuit for the magneto to work against. Shutting off the engine by shorting it does not cause it damage, it lessens the chance of failure if anything...it simple 'breaks the circuit hence stopping it.
 
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Chop-chop

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May 19, 2021
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The electrical energy that fires the coil in our china doll engines is of a passive type created by the magnet rotated by the crankshaft passing the coil of wire, this AC pulse is then amplified by the coil before being sent to the sparkplug. Now there is the other type of ignition system where a constant external voltage source is required from a battery. The components ARE NOT interchangeable. If you try to mix n match, you will either burning out things or it simply will not work.... hence I asked the young fellow to post a photo of his ignition setup so we can be sure if he is using the correct setup.
 

Karl Snarl

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Sep 20, 2019
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My CDI boxes I buy almost always turn out junk right out of the box and if not they burn out within a few minutes. I made sure I bought the supercharged CDI since on here it seemed to work pretty good. I ran diagnostics with my Ohm metere to make sure it worked but only a piece of the CDI assembly works. Any suggestions fellas?
Only way to check a capacitor discharge ignition module with a meter, is to isolate each component. Which means tearing it completely apart. The best way, Look for spark. Does it act up when warm, but when cooled down runs fine till it warms up again, when you know the a/f mix is on. if you want the best cdi for a stock to mild mod is the jag cdi, either built your own, he tells you what he used as a base and how to do it( not handholding step by step, he assumes you have the skills). He's cool like that. Or if you don't have those skill's, just buy one from the guy. They are worth the money( if you don't have the tool's and skills yourself), he use's good parts and they last forever. So many different ways to get a cdi that is not a kit cdi, for these things. Old dirt bike cdi's are sweet when you fin a compatible one. Ditch the magneto and go hall sensor and buy a powered ignition with adjustability if you want the best cdi for everything. Lots of work there though.
 

Street Ryderz

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Oct 14, 2016
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Please learn about fundamental electricals before engaging in this discussion any further. Please.

The reason the factory has a kill switch that shorts the system to shut it down instead of one that cuts off the current is BECAUSE you do not need the current to run to the switch and then to the coil etc the entire time when the engine is running. What I'm saying is, they designed it like that so that the kill-switch circuit stays neutral with no current running thru it whilst the engine is running hence LESS CHANCE FOR SOMETHING (THAT IS UNNECESSARY) TO GO WRONG. Also your suggestion of running an Inline switch also adds extra resistance to the circuit for the magneto to work against. Shutting off the engine by shorting it does not cause it damage, it lessens the chance of failure if anything...it simple 'breaks the circuit hence stopping it.
How much you wanna bet? I just finished rewiring a 125 dirtbike and got shocked from the exposed terminals under the kill switch holding it as I kicked it over! Get a meter then get a clue! An inline switch cuts the current from stator coil and then it just floats to ground if over saturated, where the stock killswitch shorts the whole system! Fundamental electronics LOL I build high power ebikes from scratch and custom controllers capable of 100v at 200 amps that's 20k in watts what have you done, this is what I do for a living and I'll speak my mind in any thread as I have here for many years!
 
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Street Ryderz

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Oct 14, 2016
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4,226
The electrical energy that fires the coil in our china doll engines is of a passive type created by the magnet rotated by the crankshaft passing the coil of wire, this AC pulse is then amplified by the coil before being sent to the sparkplug. Now there is the other type of ignition system where a constant external voltage source is required from a battery. The components ARE NOT interchangeable. If you try to mix n match, you will either burning out things or it simply will not work.... hence I asked the young fellow to post a photo of his ignition setup so we can be sure if he is using the correct setup.
You need a better understanding of how a C.D.I. system works it's called captive discharge for a reason! There is an scr in there aswell as the coils, and the rotor is the trigger after saturation.
 
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