Flywheel swap, 12v dc, and cdi conversion

Discussion specific to the various air-cooled KDX models sold in the USA
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lizardfungus200
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Flywheel swap, 12v dc, and cdi conversion

Post by lizardfungus200 »

I got a 1985 200 and I love the bike, but it has a couple drawbacks besides the old suspension, one of which is that I don’t like the idea of riding on a near 40 year old coil that has gone thru possibly hundreds of hours of heat cycles, extreme vibration, and god knows what else. Also I am tired of running a small led pod off of 9v batteries which doesn’t really do much for me when I take it on the street, so I have been thinking about possible options to get a nice new coil on the stator, replacing the old cdi, and achieving some good lighting.

Before I dump money into this thingI want to know how hard it is to get motor parts? What are some common failure points on the motor?
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lizardfungus200
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Re: Flywheel swap, 12v dc, and cdi conversion

Post by lizardfungus200 »

I got a question about how the 1985 model ignition works. I have heard that the cdi has an extra wire that comes out of it for 6 volt lighting, but mine has a cdi from a late 80s kx250, so What does the little coil do? Is it for timing the spark?

The source coil on the 85 makes about the same voltage as one from an h series, and the magnet style on the flywheels seems the same, so with the right timing I’d bet you could use an h series 5 wire cdi with that coil and flywheel. I had an old coil from 1998 kx60 and found it to be the exact same dimensions as the coil from the 85, but it is bad. Also, if you were to take the kx60 coil, and stack it on top of the little coil from the 85, it is the same thickness and provides the same coil dimensions as the aux coil as an h series, which I have a surplus of 17ga wire for. See where I’m going with this? Problem is that I don’t want to destroy the old coil, so I have been looking online for similar coils. You can buy a new exact match for like $60 online, but I was hoping to find a cheapo matching set and use those coil magnetos and make a new lighting coil, and it looks like it may be possible.

In the end my ideal setup would be a nice badass light and enough power for a couple other doodads, and a fresh ignition coil with a jaguar cdi and a honda coil, all on the old flywheel. I think that would be cool.

Right now I have the h series stator and flywheel bolted up doing some testing and the aux coil I rewound up a year ago only made like 5 volts when I turned the flywheel with a drill on high speed. That coil had some marks on it cause it got tossed around while moving, so I am rewinding it
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Re: Flywheel swap, 12v dc, and cdi conversion

Post by KDXGarage »

Check at online OEM parts stores to see which parts are unavailable.

Some have reported that a Wossner piston and rings will work. Otherwise, the piston ring pins are in an open port area.

You might want to call Ricky Stator to see what they sell.
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lizardfungus200
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Re: Flywheel swap, 12v dc, and cdi conversion

Post by lizardfungus200 »

Im more wondering if the motor has any weak points. I noticed that a pw80 coil seems like it might fit, i think I will buy one and see. Re-Rewound the coil slick nick style, getting about 8v now with a drill, Going to time the ignition and see how much it puts out at higher rpms. Kdxgarage, you did a lot of suspension work, do you know any source for fork seals, bushings, and stiffer springs?
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Re: Flywheel swap, 12v dc, and cdi conversion

Post by KDXGarage »

Most any company will have seals (All Balls for example), but bushings might have to get OEM or Race tech.

Stiffer springs, Race Tech might have some or Cannon Racecraft for custom.
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lizardfungus200
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Re: Flywheel swap, 12v dc, and cdi conversion

Post by lizardfungus200 »

Haven’t tried it yet, but the source coil from a 1995(?)-2003 yamaha pw80 will fit and only costs $30
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