replacement spark plug-rethreading

OLDSCOT · #1 09-19-2009, 08:04 PM

Had some problems with my recently purchased 2 stroke kit..Removed the plug to determine its condition and noticed that several of the threads in the head were stripped -also noted that the spark plug threads of the Chinese plug were not as protruding as those on an US plug.
Two questions- Is there an US replacement plug(long threads) that is compatible with the Chinese plug? Due to to the stripped threads,will have to install a helicoil or similar insert
in the head. Has anyone every done this and what is the procedure. Have notified the supplier and hope that they will supply a new head and a new plug but we all know how that goes.
Thanks

Pablo · #2 09-19-2009, 08:30 PM

There are several plugs that will work excellently NGK B6HS is a good starting point.

Junster · #3 09-20-2009, 12:44 AM

The threads are regular sparkplug threads. A good tool place can supply you with a heli-coil kit if they go really bad.

Kevlarr · #4 09-20-2009, 01:59 AM

Regular spark plug threads can be 7/8"-18, M10-100, M12-125, M14-125 and M18-150.

Junster · #5 09-20-2009, 03:37 AM

Ok I'm sorry I thought we were talking about the plug threads in HT motors. Not every plug made.

Humsuckler · #6 09-20-2009, 07:19 AM

there is a special tool out there for us engine builders called a thread chaser, it has a magnetic tip on it that will collect the chips on its way up.
its a must have!

Pablo · #7 09-20-2009, 07:45 AM

HT's plug threads are M14-1.25

Never tried this low cost kit:

Fix-A-Thred M14 - 1.25, Spark Plug Port Repair Kit - 2300799 | Tractor Supply Company

But the nice thing, it's so easy to take the head off.

Kevlarr · #8 09-20-2009, 10:33 AM

Quote:

Originally Posted by Humsuckler

there is a special tool out there for us engine builders called a thread chaser, it has a magnetic tip on it that will collect the chips on its way up.
its a must have!

That only works on iron heads not aluminum. It's a good practice no matter what the material the head is made from to coat the tap with a liberal amount of grease to collect the shavings.

restapukin · #9 09-21-2009, 01:41 AM

I haven't done any helicoiling for years, but, what fantastic technology!

do not pass go; move directly to a helicoil kit; it's easy to do, and gives a superb result ... a result that improves upon a virgin head...

in fact.

You'll love helicoils.

GearNut · #10 09-21-2009, 02:19 AM

I have had waaay too many heli-coils unscrew with the fastener.
Now given I did not install them, I do not know if they were incorrectly installed.
I greatly favor time serts. Properly installed they will never come out.
Antique Volkswagen and dune buggy afficinados will know them as case savers. They are commonly used in the avaition industry as well.
They are a hardened tool steel cylinder with the threads you want on the inside and special threads on the outside.
They install similar to a heli-coil, but not quite.
Due to the cost of a kit, it would be best to have a machine shop or engine repair shop install it.
The actual insert is only about $5.00 US, but the special tools are pricy.