Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I'm not sure what you're asking in post #4, but as I understand it all CDI ignition systems will have an rpm limit because of the time it takes to charge up the main capacitor (C1 in the above schematic).
i'm not sure there's much you can do. is there a way of adjusting the timing of the sensor? you could advance the timing, and up to a point, it might increase the motor RPM. if you advance the timing it may affect something else, like the engine might run too hot or use too much fuel. advance it too far, and you will have the plug firing too early and the motor will backfire and might not run at all.
The existing capacitor value has probably been chosen as optimum for use with your particular generator, coil and plug. If you increase its value it will take longer to charge, so the maximum rpm limit will be reduced. If you reduce its value then it may not store enough charge to give a reliable spark, so the engine could misfire and, again, reduce the effective rpm limit.
Your engine isn't designed for higher rpm. Higher rpm could blow the head or do other damage. Have you considered replacing the engine with a more powerful one (provided your machine can take one safely)?
Why do you think the CDI is the limiting factor in getting more speed or power from the motor? It is the fuel amount that limits the RPM and power output in an internal combustion motor. If the motor is not getting enough fuel into the cylinder, the ignition won't make it run faster. The ignition timing will change many things, but not the speed of the motor.
you may be able to make a limited increase in RPM by advancing the timing, but that is usually limited to changing the RPM with no load on the motor. when you place a load on the motor, the internal pressure in the cylinder changes as well as the stresses on piston rods, etc... what usually happens when you advance the timing is that the motor will overheat when a load is put on it. there also is no such thing as "unlimited RPM". like any rotating machinery, all of the parts of the motor have limits on how fast they can move before the increases in inertia and other mechanical forces begin breaking things. bearings and bushings begin to wear out quickly, and pistons and connecting rods begin shattering. you might be able to increase the motor speed, but it will not be long before the motor shreds itself.