heli-coils don't always work. i work on 2 and 4 stroke engines and when i get a spark plug that's stripped i use a product thats called "time-sert screw thread inserts." i don't know if this will work on your application but they work great on stripped heads for new spark plug threads. i own the tools to do it ( $200 for the kit, dont buy it unless you use it A LOT) but i dont know where you're located? maybe call time-sert and see if you can get an insert they usually run 7 bucks?!?!? if your near central ohio i could let you use the tools.... www.time-sert.com and the process is fairly clean.. let me know.... sorry i ramble...