Stripped spark plug hole

Tucker943

Bamboo Plantation Owner
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My Stihl 361 had the plug get loose and strip the threads in the cylinder. Whats the best route, long term? New cylinder or heli coil?
 
My 441s have a weird habit of doing that.
Heli coil works real well, I've never had it happen twice with the same saw.
 
For the hell of it, I'd try using a liquid gasket and cinching it down, the type that gets used in place of the base gasket when raising compression modifying saws. I'd have to check the type number of the Permabond one I use at the shop, but it does prove effective long term in a location that gets gas, heat, and pressure. A hostile environment for a liquid gasket, but if you can at least tighten down the plug to a sufficient point, it might work. The right kind is quite durable gasket material when gaps are minimal. You would have to reapply every time you remove the plug. A handy gasket to have around, even if it doesn't work for the plug. Probably won't work, but no hurt in trying if the threads aren't too shot.
 
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  • #7
I can spin the plug in the hole forever at this point. The threads are toast.
 
For some reason Tom has had problems with his 441's blowing the plug loose .Fact I looked at them and the plug isn't wibbley wobbley .I have no idea why they blow out .
 
My modded 460 had the plug come loose this season. I had it heli-coiled at the local shop, didn't last a month and the heli coil failed. I was choked, nothing else they could do for it they said. Since then I've had to drill and tap it out to a larger plug thread that matched the internal dimensions and heat range of the stock plug. Big pita.
 
The Time-Sert kit does a better job than heli-coil. My local shop did a 372 for me....a Stihl shop, lol.
 
My modded 460 had the plug come loose this season. I had it heli-coiled at the local shop, didn't last a month and the heli coil failed. I was choked, nothing else they could do for it they said. Since then I've had to drill and tap it out to a larger plug thread that matched the internal dimensions and heat range of the stock plug. Big pita.

That would work .The next size larger would be 18mm from the normal 14.Problem being most 18 mm are a lot longer in thread plus overall length .Kind of like stuffing 5 pounds of potatoes in a 2 pound sack .
 
I've never had a heli coil fail in the 40 years I've run saws.
Must have been lucky.
 
Often when I see the threads are out the plug has been run loose or over tightened.
In the few times that there are issues in material and casting the timeserts are better.
I like then as they are a tad easier to put in.
 
In my 30+ years running many a different model of Stihl (and sad to admit it, some miserable Macs in my early days :)), I only had to helicoil one 036...and it lasted many a year more with that repair. Like Stig, lucky I guess.

Never had any experience nor knowledge of the Time-Sert...I should, and will, educate myself.
 
This is the first and only time I've had an issue with the plug hole. Age ago I had to heli-coil many a top cover for the old 2 series of Husky. Those suckers would rattle themselves apart like nothing. But even then once heli coiled I rarely had a problem with them again. This plug, I'm suspecting was done improperly.
 
What is a time sert????? Never heard of that one.

Had two saws that stripped the plug holes , a 66 and a ms 200. I just got a new P&C for the 200 and scrounged a good cylinder for the 66 . I just didn't think a heli coil work in the long run.

I picked up a Shindawa saw at a garage sale awhile back with a stripped plug hole. Not wanting to spend $100 bucks on a new cylinder I might try to fix it with a time sert if someone can tell me what it is or where to get it.
 
They are every were in all auto stores or parts supply stores.
Good stuff..

Put in number 3 this week yesterday.

Learned that when cutting ir threading aluminum/magnesium mixes alcohol is a good lubricant. I used red spirits.
Not sure what it does, but it worked great.
 
If you can't tap it and clean up the threads, i would heli coil , with green locktight. Our , lycombing engines on aircraft come with heli coil inserts. They last a long time with no problems.
 
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