KDXRIDER.NET

So, full disclosure..... in central Alaska the amount of time available where the lack of sunlight and the temperature work together to require the use of a light is very small. However, I put an aftermarket led light and mount on my KDX when I did the YZ front end. I used this one:
AnXin Motorcycle LED Headlight Head Light Lamp Headlamp Kit for KX125 KX250 KXF250 KXF450 KLX200 KLX250 KLX450 KX65 KX85 Dirt Bike Green off of Amazon.
It works perfectly fine. I've had the chance recently to ride in down roads and in the woods (in the DARK!!) on single track and there's absolutely no issue using it. Sure, at a very, very low idle you can see it flicker, but at normal idle and anything beyond it works perfect and is far brighter than stock. So the only time I see a flicker is just when I bog it down below the normal idle. Even idling/engine braking down hills, the light stays solid. Did I just get lucky??

Your perception of them working perfectly fine is only because that's all you know of it. If you had it running on DC, you would see that what you previously thought was perfectly fine was actually a lot less than what it would run at its potential with. You're only able to use half the waveform if running it on AC. It's hard on the LED internal driver and they seem to live a shorter life when forced to run on alternating current.

It's cheap enough to pick up a rectifier online and replace the unit under the seat with it. There is no great magic with them although the better the quality the better the longevity. Mine was cheap and has lasted 5 years so far. I bring the original in my truck in my tool box as back up in case it ever does fail. To get rid of the flicker you can add a condenser, but I've never felt the need to.

I run an led bulb in both my kdx's and it's fantastic compared to stock, slight flickering at idle, it says on the packet AC compatible, I bought it in Thailand, if it's not available in the US maybe I could try sell and ship to the US
I've run the same bulb on my scooter for over a year