Who to go to for big valve installation?

[tillertracker]

Recommendations for CRF450 big seats and carb boring anyone?

 

[SFO]

Any qualified m/c cylinder head shop can install big seats.
I have seen a few carb boring jobs that actually performed worse than stock so I'd be careful.
Carb boring to work correctly will also require inlet boot modification or replacement with a different assembly.
What are you going to do with this project?