Originally Posted by SchwinnStingray
Just speaking in general terms here (and my background is with V8 cars) the products in question aside here, there must be something in being able to fine tune your timing to suit individual motors, 4 stroke cars for example, the factory always soft tunes cars, with no other mods, fine tuning the advance curve always improves drivability and throttle response, even more so, once you raise the compression ratio and or improve valve timing it is a must to alter ignition timing.
FWIW all the hard core bike guys spend hundreds on the best CDI to improve performance.
Two main issues are 1, spark strength and timing.
The higher the compression ratio the stronger the spark needs to be.
Timing needs to have a slightly different curve than standard and will, in most cases, need to be retarded at WOT with higher comp/rpm and improved port timing.
A standard unit may be suited to mass production but once you play with these things, head, compression, porting and the like then you will, in my opinion, need some way of improving the ignition and dialing in the timing.
Not to be argumentative about this but I run high compression heads, heavily ported jugs, very good tuned carbs and good flowing exhaust on my bikes, I just ran a non gpsd speedometer registed top speed a few days ago of 51.5 mph on one of my bikes and before it was even slightly broke I gps d 46.8 mph on that same bike, its not even running a high dollar billet head but rather a Puch hi hi 70cc moped head that cost $30 new, people claim the squish isn't right on that head and whatever yet I am getting good power and 45-50 mph out of one bike and the one bike I have with a fred head and the same basic set up is the slower of the two.
One bike is running a stock cdi and the other isn't, it could be that the better coil is helping out some on the one bike but the bike with stock coil will scream at mid 40's mph pulling myself at 215lbs
These engines do just fine with a stock unit even with compression really boosted, I have proven that with my engines and so have several others.
One fella on here blew an engine doing over 60 mph and best I remember he was running a stock cdi on that highly modified engine.
The high dollar custom units are fine but not required to have a strong fast china girl.