To illustrate the difference a good performance CDI can make, take my Skyteam ST110-6 (Honda Dax or CT70 replica), with a 107cc Lifan engine. It has been uprated with a 22mm carb, free air filter and exhaust, cylinder head breather, and rear suspension.
I have tried two types of CDI on it: The first one just removes the RPM limiter, and therefore of little use in normal circumstances. Just allows you to rev a bit higher in the intermediate gears. The second one did improve things a bit, like a little higher top speed and better throttle response, but the third one is quite incredible. The engine just howls away after passing the half revs mark and accelerates a lot better. Even the sound has changed, it's now sharper with a spine tingling tone. The only proviso is that It's wise to use a higher grade of petrol. I'm using 98 grade now. There's a danger of pinking or pre-ignition with the more advanced timing curve.

Got it from here:

http://xian.west-wire.co.uk/index.ph...od&productId=3

Looks like this. The make is POSH. This make has a very good reputation:





This is where it fits on the bike, just wedged in next to the battery:



This is the bike. I've put original Honda stickers on it to stop people asking me "what make is that". The amount of attention it gets, considering it's a 35 year-old design is incredible: