[undy]

Pick a cylinder and bring the piston up to top dead center. Pressurize the cylinder with LP air. Make sure you don't drive the piston back down in the bore, "locking" the crank if necessary. Using an "on the engine" spring compressor, pull the retainer/locks on both valves. Pull the springs, intake and exhaust. Let the air pressure of the cylinder. Note: with the piston up on TDC the valves can't drop much. Grip the ends on both valves and move them up and down in the guides while wiggling them right and left, front and back. If there's slop in the guides you'll feel it. If you can "feel" it then it's excessive. With a dial indicator you can get exact readings.. The whole process just takes several minutes.

Dave