I read this too, and I can see the logic behind it. The CDIs that come with the kits are really basic and are more suited to a 4-stroke. They don't retard the timing after a certain RPM, which is what should ideally happen on a two-stroke. The timing just continues to advance linearly as the RPM increases. This can cause the engine to run hot, and it can cause excessive force on the connecting rod bearings. With a stock HT, I doubt it would be enough to cause damage. With a high-compression head, maybe.
I have 1700 miles on my engine, and when I recently rebuilt the bottom end to replace a bearing that was going bad on the right side of the crankshaft, I checked the connecting rod lower and upper bearings and they were both fine. I had sanded the ring off my head, used thinner upper and lower gaskets, and contouered the head to fit the piston, and I get pretty high compression, but never had issues with the stock CDI except for the engine running hot. I would like to get a better CDI to see if there is any performance gain or if it runs smoother.
So no, I don't think it destroys the motors, but I do think it's a little harder on them than it could be. It seems a few two stroke scooters and mopeds also use CDIs with fixed timing, so I don't think the HTs are the only engines that have cheap CDIs like this.
Edit: The bearing that had failed was not related to the CDI or any sort of *damage*, it was a bad bearing from the beginning that just kept getting worse until I decided to replace it.
