Othen

Squirrel-hunter has this right: see if there is a bit more thread that a longer bolt might just latch on to first. I’m guessing it is not a blind hole because you say oil splashed through it.
If all the thread is stripped you could try just re-tapping it with the same size - it probably won’t work, but sometimes with aluminium the wonky threads can just be bent back into place by a steel tap, so it is worth trying to just clean it up.
If that doesn’t work then just go up one metric size and tap the hole. There isn’t much point using a helicoil as you have to drill and tap it larger anyway, and there will be more chance of dropping bits of debris into the motor when you break off the tang. I’m not familiar with the curvy, but if you are able to get access to the back of the hole without removing the engine side case you could stuff it full of rag before you drill and tap to avoid swarf getting into the motor (although I’d prefer to take the engine case off as long as it doesn’t mean a full engine strip.
Good fortune.


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