I wouldn't bother with a big bore kit. There's just not a lot of bang for your buck going all out modding one of these machines (ask me how I know
In my opinion you should bore it to the next largest size where the cylinder cleans up and rebuild it with quality parts (OEM in most cases),work the exhaust and intake ports over a little bit and install a new cam chain.
You can always throw in a hot cam or something but it's not a huge difference over stock. A more open exhaust system with proper jetting does help some also but it comes with a price and extra noise.
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