I recently had to repair a CT90 cylinder head where I had stripped out the spark plug hole and ended up using a Time-Sert insert for the repair. While expensive, I think this is the best thread repair method out there. I did a post at my CT90 blog on the process to install a Time-Sert insert and decided to share the link below to the post at my blog in case anyone else was considering using a Time-Sert insert.
Repairing Damaged CT90 Spark Plug Threads Using a Time-Sert Threaded Insert
Thanks,
Mike
Repairing Damaged CT90 Spark Plug Threads Using a Time-Sert Threaded Insert
Thanks,
Mike