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There are a few, but they are somewhat limited by part availability, and as always finances. Plus your desire and ability or your willingness to part with the quad for a few weeks, to do the needed work
You could port & flow the heads,
re-do the valves,
use a hot cam,
new piston & rings,
get a custom exhaust made,
tune/modify the carb,
What is it that you are wanting to do?
What are your performance goals?
Please, more specifically than "go faster".