I'm posting this for my brother but am familiar with the situation. He has a MS250 he purchased used. Saw ran fine up until recently. Now, it will run for a while then stall with no spark. He checks spark after a day and it is fine again and will run until warmed up. Sounds like a bad coil, simple enough fix. He orders a new one online (not sure of brand or where) and finds that he gets no spark. He re-installs his old one and it sparks fine. He calls the company and they send him another one. Same exact problem. Two new coils, neither seem to work. He's a little tired of buying coils and was hoping for some more suggestions. It consistently sparks when tested cold and losses spark when warm. Is there anything else besides the coil that could cause this? He can't believe he got two bad coils but doesn't know what else to think. Thanks in advance.