Stripped spark plug hole fixed w/ oversized adapter

[Tugboat]

I'm working on a CB350 that someone (NOT ME!!) stripped one of the spark plug holes on. They have used some sort of oversized adapter in the hole, which I'm sure would be fine if I could get it to stay. Instead it comes out with the plug and I'm not sure I can remove it from the plug without messing up the threads. I figure I'll get a new one and properly insert it so that the plug can be removed independent of the adapter.

However, I've never done this before and am not sure how you're supposed to get the adapter to stay in the head. Anybody done this before?

 

[SONICJK]

Got a picture of it?
Probably an improperly done helicoil?

 

[sphynx88]

I claim responsibility for stripping out my spark plug hole. Tried a thread chaser and 3 oversized adapters. All leaked compression, including JB welding one in. Spent 70$ for a decent head on ebay, spent a week swapping it out and never had a problem again.

 

[killian101]

I had to fix this on a 91 nighthawk...in spite everyone telling you can do this with the head still, I opted to take the head off, drill out the spark plug hole, use a helicoil with loctite 262 or something similar.

 

[Eight40]

I think those are called Timesert's ( http://www.timesert.com/ ). I race a couple 350 twins, and get Helicoils installed when building the engines. Who knows how many times the plugs have been replaced over the past 40 yrs, and it's just not worth taking a risk of getting a head fully rebuilt only to have a plug blow out. Happened once at the start of a race...and had to install a helicoil at the track. Thankfully, a fellow racer had the tool to install it. Never again!

Good luck,

TimV