Spark plug thread repair

Arne · Post by **Arne** » Fri Jan 23, 2009 11:30 am

So I've got a head that came to me with some weak threads (appears to have been cross threaded once).

Threads still work, but I'd prefer to take care of it right while its off the bike.

I took it to a machine shop to put a helicoil in, but he didn't have 12mm spark plug helicoils and also said that he wouldn't put a helicoil in it as they may work their way out.

In any case, is there a more correct way to repair spark plug threads than helicoils?

advant63 · Post by **advant63** » Fri Jan 23, 2009 1:56 pm

arne,
i have a thread insert in my hand that is a solid cylinder with a 16 m outer dia.
i called my supplier (who' s out of stock) to get more info.
he says it's made by helicoil and called save a thread or fix a thread.
my digital camera has flat batteries so i can't send a picture. if you want one i can post it later.
it is black metal with some knurling at one end, and fits ngk b series plug threads perfectly.

Arne · Post by **Arne** » Fri Jan 23, 2009 2:37 pm

advant63 wrote:arne,
i have a thread insert in my hand that is a solid cylinder with a 16 m outer dia.
i called my supplier (who' s out of stock) to get more info.
he says it's made by helicoil and called save a thread or fix a thread.
my digital camera has flat batteries so i can't send a picture. if you want one i can post it later.
it is black metal with some knurling at one end, and fits ngk b series plug threads perfectly.

Cool, thanks.

I need one for a honda 12 dia x 1.25mm pitch plug...

After a bit of reading I like these time sert things, but they're a bit spendy

http://www.timesert.com/

rngdng · Post by **rngdng** » Fri Jan 23, 2009 3:06 pm

Timeserts are expensive, but they are great!! I had a GT750 engine's exhaust bolt holes redone with them. It's worth the cost. Contact an automotive machine shop. The cost for them to do it, could be cheaper than buying the Timesert and the four tools required.

Lane

advant63 · Post by **advant63** » Fri Jan 23, 2009 4:28 pm

these are the ones i have at work. like timeserts without the collar. i hope they have the size you need.

diamondj · Post by **diamondj** » Fri Jan 23, 2009 4:47 pm

I've seen the save-a-thread kits and also "Help" brand kits at the local Pep Boys, Advance Auto, auto zone, etc.... These are pretty easy to install on your own...

Jim

H2RICK · Post by **H2RICK** » Fri Jan 23, 2009 10:09 pm

I vote with rngdng on this one. We use Timeserts in our shop and NO comebacks. Those suckers will NEVER come out like Helicoils will. Well worth the bucks, IMO.