I've rewired at least 20 of these damn 110cc / 125cc China bikes and have always been able to get them running but this 1 has me tearing my hair out. I've had it up and running twice now in the last month but after I shut it off I am unable to get spark again. It seems like it's just blind luck that it ran in the first place. First time, after the initial wiring, it stalled out while adjusting the carb and I tried for 2 weeks after with no luck. Finally I decided to just order a new 5pin cdi, stator, and ignition coil. Wired those up and got spark. Once I put the plug in and made the wires pretty, I had no spark again. I am now on my second set of new stuff and still no spark. Note that I am not hooking up anything but the 3 wires from the stator and cdi and of course the ignition coil. So no kill switch. I've even tried the harvey Spooner dc cdi box trick and it does spark but only once as soon as I hit the start button, then nothing unless I let off and push it again. At this point all I can think of is that something is wrong with the flywheel but that doesn't make sense to me. Could timing be causing it not to spark? Could the flywheel itself be causing it? PLEASE HELP

 

The CDI must not be getting a signal from the trigger coil to tell it when to spark. Check both resistance on trigger coil at CDI plug, and what AC voltage it puts out when the engine is spun on the starter. Try swapping the trigger coil with the old one if you don't get much of a voltage, and see what that produces.