I have a Briggs and Stratton Model 252707 engine in my lawn tractor. I need to know how to adjust the intake and exhaust valve. Do you measure for clearance at top dead center on 1/4" down after top dead center. Is the procedure the same for both valves. Reason I'm I'm asking is my engine is hanging up when trying to start it with the electric starter. Battery is fully charged, it seems like the compression is stopping the engine from turning all of the way over. With the plug out it turns over fine, no compression. With the plug in it seems to hang on a regular basis. When it does hang when the stater disengages it seems to kick back counter clockwise. Have done a compression and leak down check. Compression is good, maybe even a litle high. Haven't checked it again recently, am about ready to put the lawn tractor out of its misery. Stopped running last year as I was putting it away. I have managed to start it twice it started this no start condition. If I remember correctly one or both times I had to use starting fluid.