Stihl ms251 Spark plug thread repair

[heimannm]

These spark plug inserts by Helicoil are solid rather than the spring type for their typical thread repair and include the tool to swage them in the block.



Mark

 

[rocketnorton]

Interesting concept but what does this do to the heat range of the plug now that it is surrounded by much more steel than was intended in the original application?

afik, plugs dissipate heat accordin to length of porcalin insulator.

 

[Conquistador3]

Interesting concept but what does this do to the heat range of the plug now that it is surrounded by much more steel than was intended in the original application?

I had a Heli-Coil repair on a Honda engine. OK, it was a four stroke but I used exactly the same spark plug as before for years before selling the engine (still working). Never had a single problem.

 

[Weesa20]

I ended up using the timesert spark plug kit in 10mm 1.0. Pricey but worked perfect. Has a step tap so it ensures straight threads. No drilling. Couldn't gone better. I couldn't find the helicoil solid inserts in 10mm. Everyone had the 14mm only.

Weesy

 

[rocketnorton]

got it fixed, that's the main thing.

 

[smallengineredemption]

Definitely pull the cylinder, I don't like helicoils I much prefer the insert type like timesert. Very easy to use, they have a piloted reamer that threads into the existing plug hole and it cuts and threads the hole for the insert. Thread in the insert with a little sealant on the threads and use the expander tool to expand it, let the sealant cure overnight and get back to sawing.

Where to purchase timesert? Think this will replace a helicoil kit on a 441 in which inner helicoil threads blew but outer are still in tact

 

[heimannm]

Trust me, you won't purchase a Time-Sert kit to make one repair. This Amazon listing is for the tools only for repairing a washer seat type plug, the inserts are more. You can find the washer seat type inserts for $4.00 to $5.50 each.

https://www.amazon.com/Time-Sert-M1...ocphy=9018116&hvtargid=pla-570903485897&psc=1
I have a number of the tools available (step tap, seat cutter, guide) but lacking the driver to operate the seat cutter. I clever fellow could make one with a lathe and a milling machine.




I am offering the kits as shown above for $35 + shipping. The guide is actually 92130...

Mark

 

[smallengineredemption]

Trust me, you won't purchase a Time-Sert kit to make one repair. This Amazon listing is for the tools only for repairing a washer seat type plug, the inserts are more. You can find the washer seat type inserts for $4.00 to $5.50 each.

https://www.amazon.com/Time-Sert-M1...ocphy=9018116&hvtargid=pla-570903485897&psc=1
I have a number of the tools available (step tap, seat cutter, guide) but lacking the driver to operate the seat cutter. I clever fellow could make one with a lathe and a milling machine.


View attachment 1045633

I am offering the kits as shown above for $35 + shipping. The guide is actually 92130...

Mark

Find me the links to the inserts I might buy your kit. And do you know what aize I should use on the 441? 10mm 14mm I've done plenty of helicoil thinking of stepping it up bc you don't typically do a second helicoil. The time serts are installed differently I am told. It is a new process to me. Any help or knowledge is appreciated

 

[heimannm]

The tools I have are for M14x1.25 spark plug threads only. The correct insert for a washer seat plug with 3/8" threads would be these:

https://www.ebay.com/itm/280789601672
Google Time-Sert or search eBay for Time-Sert Spark Plug and you will find many different inserts available. The complete kits are most often only available directly from Tillman or perhaps from some authorized distributors like Thread Doctor in the eBay link.

Mark

 

[wildwes]

https://www.autozone.com/test-scan-...ls-spark-plug-thread-repair-system/141511_0_0

This is the kit I have used successfully. I have done it without pulling the cylinder, although it is much better to bite the bullet and pull it.

 

[heimannm]

That is essentially the same as the Helicoil Sav-A-Thread kit.

I've only repaired a few stripped plugs with that kit but they have all been quite successful.

I acquired the Time-Sert tools in a large lot of McCulloch parts, I haven't had the need to use them since I discovered them but I do have an assortment of inserts on order.

Mark

 

[Captain Bruce]

I used a Fix-A-Thred Kit on several 251's.
Kit #25628. Its a M8-1.25 tap, that uses a 21/64th bit to tidy the hole. Super simple. I keep a spare and a handful of inserts, just for the 251. Good Luck.

 

[wildwes]

That is essentially the same as the Helicoil Sav-A-Thread kit.

I've only repaired a few stripped plugs with that kit but they have all been quite successful.

I acquired the Time-Sert tools in a large lot of McCulloch parts, I haven't had the need to use them since I discovered them but I do have an assortment of inserts on order.

Mark

The insert in that kit is more like a time-sert- it is a solid steel insert that is serrated, and that is flared out mechanically into the hole. It is not like a helicoil, which is a spiral wrapped piece of wire. I have used both, and that kit is more permanent than a helicoil.

 

[heimannm]

Wes - you may need to review the full thread to catch up.

Mark

 

[wildwes]

Wes - you may need to review the full thread to catch up.

Mark

My apologies- I just looked up the sav-a-thread kit, and you are correct, they are basically the same. I Thought you were referring to the traditional helicoil with the coiled wire insert.
And the time-sert is a better method for sure, but the kits like I linked, or the sav-a-thread also work well on a budget. I have used them and never had any trouble with them. If I were repairing a high dollar saw, I would use a better kit. Usually I am using them on beater saws that someone else has damaged badly, or cheap saws I am working on for one of my students.