Strip spark plug

[dinoedwards]

Removed this plug and found this, going to chase it with 14mm tool, does this look that bad? Looks like I can save it without using helicoil.
Kohler 25hp twin, sux because I just took them out last week and it was fine, wtf?
Replacing with Champion 71/RC12YC

 

[5030]

Always apply a small amount of never sieze to the plug threada no matter what engine they go in..Prpblem with chasing the threads with the head installed is you will get swarf in the combustion chamber and that is not a good thing.

 

[DarkBlack]

I never use anti-seize on spark plugs, and never will. If you feel the need, make sure you compensate on torque values, and make sure it’s an electrically conductive version

 

[tomplum]

I'd chase it. Ground the spark plug wires and crank it over before installing the spark plugs.

 

[ericm979]

It it is damaged beyond use the threaded inserts (not a helicoil) work pretty well.

 

[Mudfarmtruck]

I always find warming the motor up before a plug change helps. You can use a penetrant, make sure around the area is clean before you pull the plug . The biggest thing is do NOT over tighten then . Also check your gap. I personally wouldn’t use champion , but that’s a personal preference.

 

[SPYDERLK]

Removed this plug and found this, going to chase it with 14mm tool, does this look that bad? Looks like I can save it without using helicoil.
Kohler 25hp twin, sux because I just took them out last week and it was fine, wtf?
Replacing with Champion 71/RC12YC

Thats aluminum right?
Take a new or unaffected plug and see if it will thread in by hand at least a thread or two. If you get resistance wiggle it a little and see if that will allow a good start and/or a little more progress. If you are successful in getting a couple turns by hand it is threading correctly. Take it out and do it again. Same? Good.

Now remove it and clean everything -- WD40 and airblast. Apply anti seize to the plug and try it again. Same or better? Good. Put a little anti seize at the head thread entrance and redo hand threading. Maybe turn it with a wrench another turn. Remove and repeat. It should feel better and go further. At that point you could probably just screw it on in.

I intentionally avoid chasing because a full thread will find its correct registration better vs a tap accidentally cutting a new registration. Also a tap, even starting right, will remove some aluminum material that is still useful. Whereas the steel plug thread with antiseize will just form it back into position.

 

[skipmarcy]

All you have to do to chase those threads is put some good old axle grease on your tap - and even if you were to get a tiny bit of aluminum in the cylinder, it will be gone quickly right out the exhaust valve.

Many years ago I bought a 1962 Olds F85 with the all aluminum 215 c.i. V8 for $25 because it had a rear stripped spark plug hole. It used the conventional 14mm plug like most GM. I took an 18mm tap, greased it up good and re-tapped the hole to accept the 18mm plug that Ford used in so many of their engines of the time and drove that car for the next many years before selling it.

I ALWAYS put a little anti-seize on spark plug threads, helps avoid gaulding like you have there on that spark plug.

 

[CATRAT66]

Looks like you over torqued them two weeks ago.
The remedies or a combination of them suggested should work for you.
Stuff like this is what mechanics not parts changers do.

 

[5030]

People always tend to over torque spark plugs and install them with dry threads which is an invitation to galling or cross threading.

If the spark plug has a crush washer on it, 1/2 turn past contact is always enough and if it's a tapered seat, that also applies but again always use never sieze on any plug, not a lot, just a bit on the end of the threaded portion as the end of the treaded portion will distribute the never sieze as you screw it in. Makes removal much easier as well. I've never stripped threads in a spark plug hole in my life and I'm 76 years old.