most small engine point gaps are about .020 inches with + or - .005 (about .5mm + or - .1mm(about the thickness of a business card)). changing the gap changes the dwell (the time the points are open) which changes the timing. so if you want, you can mess around a bit with the gap to see if it runs better with a smaller or larger gap. if you have timing marks on your flywheel, you can set the cap using a continuity tester or ohmmeter. connect one lead to ground, and the other to the moving point. when you line up the timing marks, the continuity should break. making the gap smaller makes the spark occur later and vice versa.