There are a couple of aftermarket CDI's out that use an adjustable board and larger aftermarket coil but they are aimed at high compression race engines and run like $80.
Most work by changing the RC timing circuit, heck I have my own little PC board etched and parts on hand I will be testing soon with the same features but unless you are going high performance for racing you can do what I do as standard on every 2-stroke build to get a little more performance:
1. Replace the stock plug with an NGK 5944 Iridium plug (BPR*HIX) where the * is a heat number between 5 and 8.
The lower the number the more heat you engine retains.
Here in Arizona I run 7's for the most part but in August when it's 110+F for a rider riding a couple hours at a time an 8 is in order to keep the engine cooler. Just note that if you go too high a number for the conditions you will foul plugs as it's the heat that self cleans the plugs.
It's winter now so if it is cold where you are a 6 or even 5 would be better but running too hot of course is not the way you want to go either, as cool as you go without fouling is the ticket.
2. Replace the junk mag to coil wire with some insulated 16g wire.
I use indoor/outdoor speaker wire I buy at a $1 a foot on a 50' spool as it looks good and bends well but you can cut a chunk out of any 'universal' power cable for PC's and TV's and such.
The object is to direct wire the magneto to the coil with nice fat continuous wire for less losses.
My speaker wire has red and white internal wires so don't get confused by colors, pick a color for your blue and black wire matches and solder them right to the mag.
At the CDI I just cut the little shrink wrap where the wires come out back, cut one wire very short, the other a little longer and match up the individual lengths from my wire.
Then I attach the kill button to the same connection and just cap it off with a $.50 plastic hobby box and glue it on.
I got fancy on many new builds and wired in an ignition keylock switch as well.
In that case I fill the box up with epoxy so the switch can't be defeated and trying to will break the CDI wire rendering it useless so the would be thief has to buy and re-wire in a new CDI.
A keylock won't keep the bike from being pedal ridden or carried away, it will prevent the thief for firing the engine ;-}
I used to do keylocks in the plastic box on all my builds and even sold all the parts to do this awhile back as simple parts in a bag for $17 delivered anywhere to completed units with CDI for more but ran out of parts.
I recently replenished my supplies in bulk and will be offering some new ignition kit options for sale early next year that may be pretty cool, though I can work building new motorized bicycles year-round here I tend to like doing the simple indoor stuff during the holidays.
