An insert may make the plug run a little hotter but who cares? Just as long as the plug doesn't foul out it's not factor. Threaded inserts in cylinder heads are very common and I've never heard about anyone having troubles, other than sometimes the inserts pull out.
As far as chips falling onto the cylinder causing troubles, this is unlikely unless a whole lot of chips fall in. Grease the tap and only a minimal number of chips will make their way inside.
All this said, MisterCinders needs to decide how far he wants to go with fixing the engine. Simply installing the insert back in place might be all that's necessary, or maybe the cylinder/rings are trashed. Hard to say for sure. Personally, I'd try the easy route first and see how it turns out. You can always pull the head if necessary at a later time.
As far as chips falling onto the cylinder causing troubles, this is unlikely unless a whole lot of chips fall in. Grease the tap and only a minimal number of chips will make their way inside.
All this said, MisterCinders needs to decide how far he wants to go with fixing the engine. Simply installing the insert back in place might be all that's necessary, or maybe the cylinder/rings are trashed. Hard to say for sure. Personally, I'd try the easy route first and see how it turns out. You can always pull the head if necessary at a later time.
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