Is the head & valves salvageable on my intek 65

Hi all.
I've been experiencing blowback through carb and lack of power on a ride on I acquired a while ago. I assumed leaking inlet valve and decided to investigate. I've been using valve grinding paste but think the head and or valve may be too far gone. See pics.
Should I carry on grinding or look out for a head?
Thanks in advance.

No pic's posted..
 
If the head is currently off the engine, re-install the valves and spark plug (normal tightness).
 
Flip the head upside down and fill with a very light viscosity liquid. 
If the valve(s) are leaking, the fluid will leak out thru a/the ports.
 
No fluid should leak out.  Also, check for straightness with the head surface.
 
I gather you've never heard the engine correctly?
 
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The sealing surface, per your pic's, aren't sealing.
 
All that carbon has to be removed the valves(s) and the valves re-seated.
 
I'd also check for bent valves, especially if you can't get a good sealing surface..
 
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