Can a stripped thread repair be repaired?

[NewToStihl]

I just acquired a saw with a cylinder that had had the spark plugs repaired with a Sav-A-Thread at some point in it's life and now that has been stripped out (previous owner must love to wrench that plug in!). I assume that means the cylinder is shot, but I would love to be proven wrong! I've never ceased to be amazed with some of the tricks & tips you guys have tucked away.

So, is there any way to make a quality repair in this scenario? I believe I've heard of welding a stripped hole shut and re-tapping it. It's an MS460 though, nothing rare or hard to replace, so I don't think it would be worth the cost and/or trouble of making that happen. Anything else?

Thanks!

 

[Jacob J.]

Apart from welding and re-tapping, you can go out to a larger thread size for a plug that matches. I had to tap an 066 jug for an 18mm SBC spark plug once for a logger's saw. It lasted for two years until they ran the saw over with a skidder.

 

[NewToStihl]

That's interesting. I was expecting to hear something crazy about tapping it farther out and using some sort of a reducing bushing, but a larger spark plug never occurred to me...

 

[pioneerguy600]

The bushing will work also, been there,done that.

 

[AKDoug]

You could probably get that Save-A-Thread out and put a new one in. Some heat and a big e-z out screwed into it should back it out.

 

[NewToStihl]

You could probably get that Save-A-Thread out and put a new one in. Some heat and a big e-z out screwed into it should back it out.

Unfortunately the Sav-A-Thread stripped out of the aluminum. It's not a matter of bad female side threads being stripped in the insert.

 

[AKDoug]

Unfortunately the Sav-A-Thread stripped out of the aluminum. It's not a matter of bad female side threads being stripped in the insert.

Gotcha. Better go with Jacob J's plan, then.

 

[NewToStihl]

It's definitely looking like a larger plug is going to be the way to go. So, I guess I just need to cross reference and find an 18mm spark plug with the same heat rating as the OEM plugs?

 

[AKDoug]

Ask Jacob, the 461 uses the same plug as a 660

 

[Jacob J.]

Ask Jacob, the 461 uses the same plug as a 660

It's been so long I don't remember which exact plug we used. It was in 2000.

 

[AKDoug]

I've always wondered about this stuff. Glue that insert back in there. http://www.newpig.com/pig/US/high-t...0651&ddkey=http:US/ap/PPCHDEP25/PPCHD25GC250O

 

[NewToStihl]

I've always wondered about this stuff. Glue that insert back in there. http://www.newpig.com/pig/US/high-temp-weld-pty246?squealDealCode=PPCHDEP25&code=PPCHDEP25&orderId=2365651&catalogId=17208&autoAppliedPromo=true&errorViewName=CalculationCodeErrorView&cm_mmc=R-_-PLA-_-Go-_-PTY246&URL=/pig/US/high-temp-weld-pty246&langId=-1&page=/pig/US/high-temp-weld-pty246&view=/pig/US/high-temp-weld-pty246&set=PPCHD25GC250O&gclid=CLjYidKi0cICFUeEfgodN00A7w&storeId=10651&ddkey=http:US/ap/PPCHDEP25/PPCHD25GC250O

I definitely would be willing to try it if this was a saw I planned to keep. This one is just a flipper, so I don't want to use anything I don't have experience with.

 

[LowVolt]

Do they make keyserts this big???

 

[ChoppyChoppy]

IMO not worth the hassle when a new jug is pretty cheap.

 

[NewToStihl]

IMO not worth the hassle when a new jug is pretty cheap.

I'd agree when it comes to having it welded, but to simply tap it to 18mm and use a larger spark plug is very little hassle. Except for figuring out which spark plug...

 

[ChoppyChoppy]

Yeah, I was talking about keyserts and/or welding. Sure for a saw that cylinders aren't make or are $$, but a 460... I think even Walmart has a few cylinders on teh rack!

 

[LowVolt]

IMO not worth the hassle when a new jug is pretty cheap.

Yeah, I was talking about keyserts and/or welding. Sure for a saw that cylinders aren't make or are $$, but a 460... I think even Walmart has a few cylinders on teh rack!

 

[toolmaker]

If it were mine, I would figure a way to do it. Especially if the jug was still good and worth keeping.
Someone above mentioned a reducer plug. That's exactly what I would do. Of course, it would have to be custom machined.

I have been a Tool and Die Maker for over 35 years, it's my curse................

Every single thing I own has been modded or improved in some way or another.

I buy custom, aftermarket engine and clutch parts for my Can Am ATV's. I modify them even before they are installed on my bikes.
There are several aftermarket engine and clutch companies in the U.S. and Canada that offer parts for Can Ams'. They actually send me prototype parts, I test them, modify them, and return the parts. They save the final changes, put the parts in to production, and offer them for sale to the public.

 

[pioneerguy600]

I've always wondered about this stuff. Glue that insert back in there. http://www.newpig.com/pig/US/high-temp-weld-pty246?squealDealCode=PPCHDEP25&code=PPCHDEP25&orderId=2365651&catalogId=17208&autoAppliedPromo=true&errorViewName=CalculationCodeErrorView&cm_mmc=R-_-PLA-_-Go-_-PTY246&URL=/pig/US/high-temp-weld-pty246&langId=-1&page=/pig/US/high-temp-weld-pty246&view=/pig/US/high-temp-weld-pty246&set=PPCHD25GC250O&gclid=CLjYidKi0cICFUeEfgodN00A7w&storeId=10651&ddkey=http:US/ap/PPCHDEP25/PPCHD25GC250O

Just want to stick this in here, whatever device is used to correct the thread must be a tight fit to the remaining cylinder head so that it can disperse the heat built up from and around the sparkplug. Most of the certs I have used were too loose fitting for my liking so I modified the threader a bit to make the inserts just a bit difficult to screw in, same with a custom made plug/bushing. A tapered pipe thread on the OD of the bushing would work much better than a straight bolt thread but would require a bit of fine tuning to get the inner surface of the bushing set at the correct depth, think grinding to length.

 

[ChoppyChoppy]

Well...

Cylinder is about $65 (aftermarket)

Vs repairing... I'd charge the customer probably an hr (R&R the cylinder and repair the threads) plus parts so there's $90... so maybe $100ish and it's still a patch together cylinder.
To replace the jug, probably around $100 total.

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