I did something stupid and installed a wrong spark plug in my rear cylinder . I got it out but it looks like 1\2 my threads are gone. What can I do? thx Bob

 

pull the head and have a time insert installed or replace the head. I would not trust a helicoil in a plug hole. I guess if you look at the silver linging you can just put a set of hi-po heads on while you got her apart.

 

yup, some say you can do it with the head on the bike. I wont though, even go into an argument with a customer because i refused to........I also feel timserts are better.

 

I've used both and installed both while the heads where on....I machined compression release holes with the heads on. You put the piston to TDC on the exhaust stroke, remove the pipe and install the hose to the shop vac in the exhaust port, grease up the Drill Bit and the Tap and your off to the races.........never had a failure.

 

These are a set of hq heads [:@]. Don't ask how I got a wrong plug. But I still want to do it right. Timesert? I'll have to look into this more. Had to walk away yesterday. thx Bob

 

cabo,

I know hindsight is 20/20 but how in the world did you not notice that the plug was harder than normal to get in there? That is when you should have stopped.

 

Timeserts have two locking pins that are pressed/punched into the original mat'l to lock the insert.
Do a search.

 

I been using Helicoils for years on hacked plug holes in aluminum heads. Helicoils are stronger then the stock threads. I like the vacuum on the exhaust idea. - BUT you could just try tightening a new plug and see if it holds. There are way more threads then needed on a HD plug (look at the thread length on a briggs and stratton lawn mower plug)

 

thx Everyone
I'll be pulling her apart tonight. I'll see how bad it really is.
thx Bob