If the bike is 100% stock then you will struggle to keep up with cyclists. The MC28 is quite heavly restricted. Most of the information you need can be found in the Tuning section of the site.

A quick run down of what you need to do though is.

Wire splice
Derestrict the stock pipes or fit race pipes

Or

HRC card
Wire splice
Race pipes
HRC jet kit

This will see you from around 40hp (stock) to 55hp (option 1) to 60hp (option 2).

I admit I'm not that in the know when it comes to '28 as they are.. lol a bit weak.

I'm sure Fontyyy will put me right if I've gone wrong anywhere (in the post fontyyy not in life thanks).
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If I have to take the carbs off once more...