Road racing a 650R- Need more power!

I need advice from those who have been there and done that-

I am road racing with an '01 XR650R engine. I have the full HRC kit, custom airbox, Big Gun exhaust, open intake manifold, and the stock carb (with the HRC needle, 68 idle and 178 main).

I want more top end power, but I wasn't planning on getting into the inside of the engine again until it needed to be rebuilt. I also don't want to lose reliability.

Has anyone gone to one of the bigger flat slide carbs? I was thinking about a 41-43mm Mikuni or Keihin. Is head porting necessary to take full advantage of one of these?


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