This gets a bit complicated to explain but here is some general info . If your cdi has a rev limiter and you are hitting the rev limiter, you can get a cdi that has an adjustable rev limiter, however, the timing curve will most likely be different . You can map/plot the timing curve to some degree if you put degree marks on the flywheel and have a tach and timing light . This will allow you to see the difference between the curve in the two cdi boxes . In general, if only the cam is changed to a larger one and all else remains the same, you will get more power everywhere if you increase the timing throughout the entire rpm range.
If you don't have a mechanical advance unit and don't have a rev limiter, you can increase the timing throughout the entire rpm range by advancing the flywheel with an offset key or removing the bump on the flywheel and advancing it or advancing the pick up if there is some way to do it on the particular bike you are working on.
If you have a mechanical advance unit you can simply modify that to get more max advance . If you want to change the timing curve on a mechanical advance unit you can bend the spring stops slightly and/or try different spring.
Since incorrect timing can cause increased heat and/or detonation etc, it is important to monitor these things, and if you don't have a lot of experience with changing timing curves it would be helpful to install a temp sensor and ideally also a detonation sensor, however, detonation sensors are very expensive . A spare piston might also come in handy.
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f, vedegree s you have a tachpat n aftall you need to do is Max revs are cntrIf you