Risky business…
I agree with Adam!!!
AND : there are hopefully no explosions in the engine ! … it’s a burn 🔥!
there is also the possibility that the “dirt” , if it’s that , stays in the same position and just gets pounded into the seat on the head or on the valve and it will not get better! Then, you have multiple possibilities of failure!
your problem may even be a not proper installed valve seat… If that’s the case, you are actually lucky that you discovered it before you fired it up!
I would bite the bullet and open it up!
There can only be two answers:
the valve seats proper
or
it doesn’t!
there is no… almost good!