Adjustable CDI project

[Kx200x]

I’ve got a 99kx125/kdx200 e series hybrid. Originally just supposed to be a woods bike. I’ve only just finished it and I first rode it at the Mx track and liked it. It has boyeson reed valve, custom exhaust similar to fmf, 35mm carb 1173nt needle(if that make sense). I think the head is milled. I bought the bike with a bad engine and picked up an entire unit as it’s very difficult to find powervalve parts. So as I put the new engine in I was swapping the stator and noticed it was fully retarded. I started looking up adjustable CDI units and people have sold them but doesn’t seem like they are any more. A member Jaguar has a lot of info on it. I was thinking maybe we could start a thread to get the info together for the DIY guys. Info on what parts are needed to be changed and so on and so forth.

[Kx200x]

From a Jaguar post on another site
“The negative voltage is 4.5 at idle (with the standard 16 ohm pull-down resistor in the CDI). The previous rewound coil was 5.5 v at idle (with 18 ohm resistor). The pull-down resistor controls the negative voltage level which affects the timing curve.
So to experiment I installed the OEM coil and replaced the pull-down resistor with a resistor and potentiometer which could vary the resultant resistance from 16 to 22.5 ohms. That pot was taped to my gas tank so I could vary it while riding. Also the 4.7uf CDI timing cap was left standard for the first test session. It seemed to have the best powerband with the resistance close to 21 – 22 ohms. But the impressive mid range boost of my previous setup was missing. Then I added .5uf to the 4.7uf timing cap (making it equal 5.2uf) and tested again and that oh-so-lovely mid range boost came back when the equivalent resistance was in between 20 and 22 ohms.”

[Kx200x]

I’m not exactly sure what potentiometer to get or the correct capacitor. Also want to add the 2001 cr125 coil as it has a higher output.

[Jaguar]

I'm now starting to make the KDX Performance CDI available again, so let me know if you want one. www.dragonfly75.com/moto/KDXCDI.html

[billie_morini]

KX200x, the summary you shared falls into the category of "Don't try this at home, Kids!"

The summary describes how Jaguar empirically determined operating parameters beneficial to know when designing & fabricating the CDI unit he makes & sells.

One common positive, whether we're talking about CDI units made by Jaguar and SS109, is these are made specifically for KDX"s by KDX enthusiasts. This, in my view, makes these CDI units more desirable than generic or universal units made by larger fabricators.