A question on repairing spark plug threads

[Flywelder]

I would like to repair the spark plug threads on my Poulon chain saw. The metal looks like aluminum but aluminum rod will not stick.
I tried JB Weld, and another type of liquid metal, and these both did not work.
i cannot find a heli -coil that will accept spark plug threads....perhaps I have not find the correct one?
But welding the hole smaller then drilling and using the spark plug tap / thread chaser i have I think would be better...but i have not found a rod that will stick..what shall i use or what other methods have you found to work well?
Flywelder
10-26-08

[ElGuapo]

There are special Heli-coil inserts and taps for spark plugs.

[David R]

Try NAPA or another parts store. They have thread kits.

David

[mrmikey]

Chainsaws, or at least any I've repaired, are magnesium.
You'd be better off going the helicoil route as they are available and there'd be less chance of doing damage to the head, aka warpage.
If you deo decide to weld it, watch your ground, make sure the area is clean. Magnesium is very prone to arcing if you don't have a good connection to ground, ask me how I know.....Mike

[Flywelder]

Great ideas guys!
thanks to all!
mrmikey, would you share how you know about the arcing tendency?

[Donald Branscom]

They also sell spark plug hole thread chasers.
Try JP cycles.com

[Fabtec]

I have used Time-Sert to replace spark plug threads. It is very common to lose threads in aluminum when steel threads are used on either a fastener or a spark plug!
http://www.timesert.com/

[mrmikey]

mrmikey, would you share how you know about the arcing tendency?

Just make sure you have a good, clean area under the ground clamp.
On the first chain saw I repaired, (too long ago) I was being a smartass and trying to impress the guy that brought it into the shop. I clamped the ground onto the frame, if I remember right it was the handle that was cracked and proceded to weld it up. I though as I was weldingg it the arc sounded funny and the heat seemed to be fluctuating a bit but I never thought anyhting of it that is until I was finished.
Where I had clamped the ground was still half painted and the ground wasn't 100% thru the area that was, I ended up melting a hole thru the other half of the handle which didn't go over too well needless to say.
I don't know if magnesium is a bad conductor of electricity or if forms an oxide theat is harder to get a connectio thru but to this day I'll always grind the area where the ground is connected.....Mike

[papasloan]

I agree with Fabtech. Dont use a helicoil. Use the Timesert insert,it is a sold steel piece not a coil. A helicoil can unscrew especially as short as plug threads are.

[Flywelder]

Thanks for the new information guys!
I have called around in my small town for the Time inserts , no one has heard of them, and they all offer heli-coils to me, along with : " that's what all the machine shops use to replace spark plug threads, ..i ant never heard of then backing out, you do know you use red thread lock with the heli - coils?....you don't need anything else son, i got what you need, you just come on down, we'll fix you up"

So now my question is, I need some suggestions on finding time inserts.

thanks for sharing the info mrmikey, that was good knowledge to pass along, thanks.

[prop-doctor]

napa: carries a similar product

[Mondo]

Check out this web site:
http://www.pendergrasstool.com/kits/spark_plug.htm

No matter what repair method you choose you shouyld have the cylinder head off so it can be handled carefully, cleaned, and the inside of the cylinder and intake kept clean. This requires a gasket kit already. So I am compelled to ask this next Dumb Question: what is the price of a replacement cylinder head for this chainsaw compared to the price of a Timesert (or other thread repair kit) plus your time mucking with this?

-Mondo

[denrep]

Originally Posted by Flywelder

...I have called around in my small town for the Time inserts , no one has heard of them...

I'm pretty sure NAPA sells them.

This may be another source:
Attachment 24646

Sometimes if the threads can be saved for just one more use, a non-fouler adapter can be put in the head:
Attachment 24647
Then the threads never have to be turned again.

Another desperate -man option is to drill out to use a larger 18mm plug.

Good Luck

[Timberwolf]

There are some short reach 18mm plugs from aviation motors, but not the kind of stuff you will find at an auto parts store.

If it is one of the green poulans like a wild thing or wood shark then the jug is a very high sil casting well over 12%. They run a bare aluminium bore and chrome plated piston, so not easy to weld.

Option you can bore and tap it out to 18mm and then use a screw in spark plug adapter, but the edge of the spark plug hole is very close to the squish band transition in the head so I am very doubtfull you could use an 18mm plug or 18mm plug adapter.

Also the reach on these plugs is very short so you only get 4 or 5 threads engauging at best, does not give much purchase for an insert or Heli coil.

I have mannaged to weld chainsaw jugs with success, but I suspect they are a different alloy than what you are working on. 4047 is closest common filler for these high sil castings, but 4043 not bad, 5356 is not what you want as it is not going to take the temperature.