how to free stuck valves

My 17a starting engines two center valves are stuck ( l left the carburetor off for too long) what is the best way to unstick them without taking the head off of the engine. Any body parting out a 24 or 25 ccu around Kansas? Thanks

if you have access to the valve stem under the access cover you can usually clamp on to the end with needle nose vise grips and wiggle them back n forth or use a standard screwdriver as a wedge between the lifter and valve to push them up more.

Thanks I had thought of using a dowel rod in the spark plug hole be am worried about bending the valve. I will try your idea as it would put a straighter
force on the stem.

I put feeler gauges between the valves and push rods and turned the engine over, then I took a brass punch to knock them back down (through the spark plug hole. put it back together and it started first turn. My next question is has any body had the main engine full of water (4 gal on this D7)
and what did you do before attempting to start the engine? I plan on taking the oil pan off to inspect and clean up the gunk--I also will inspect the
oil pump. The valve train has some rust so I will take it apart and clean that up. What else? Thanks