I have an original 1974 Trail 70 that ran prety good but had stripped spark plug hole. I carfeully installed a heli-coil (w/o removing the head). Cleaned out all debris w/ cotton Q-tips, prior and during the instalation of the heli-coil. I put in new NGK plug. Now it will not start. It does have good spark (I checked with boot on and plug against head and saw a good spark). I have good fuel as well. When I kickstart, it feels like the same compression as before but not sure. Is it possible the plug is not deep enough now? It seems to butt up against the head as it did before. Just a thought. Any ideas or help as to why it won't start is much appreciated!