Chainsaw Repair

Okay, the mono seal works on the fuel tank. Now to the next issue. Bout to drive me wacky (er)
Checked/cleaned all my ignition components ( points). Reassembled and no spark. Took it down again and checked everything again. Checked continuity of points as each piece goes on. Without starter installed. - good continuity; even rotated the crank. Installed starter, sometimes good and sometimes not. Once, I discovered that when I tightened the front screw on the starter I lost continuity. Loosen screw half a turn - good. Tighten - bad. Did this several times. Took down and rechecked everything. Put different wire in from points to coil from a parts saw; no joy. Refiled points; same deal. I've had the ignition and all components apart at least half dozen times. Points look good, nice and shinny, though worn. I'm not giving up but would appreciate constructive comments
Thanks much