Timesert insert size

I had the misfortune to have a spark plug blow out of the head recently.  Apparently either I damaged the threads installing the last set of spark plugs, or someone in the bike's previous life (which has been long and sorted) did.  Either way I need to either drop the motor and replace the head or buy a timesert kit.  I have ruled out helicoils after reading too many negative comments about using them for spark plug repair.

10mm x 1.0 is the thread I think, correct me if I am wrong.  But how long of inserts do I need?  The kit comes with 15mm, but there appear to be shorter ones available.

Thanks in advance for your help!

Douglasthecook has been there......   so when he sees your post...... :tour:

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Answered my own question. For anyone else searching for the answer to this question: To determine the correct Time-sert insert length, measure from the end of the spark plug thread to the spark plug washer.

You don't need to drop your motor to do the repair. I simply pulled the heads off with the motor still installed, and completed the repair on my work bench.