[MS 193 T] New-to-me unit, suspect the block's spark-plug-slot is compromised but cannot be sure (pics in-post!!)

eyehearttrees

Active Member
Location
Tampa-Area
tl;dr-- Pretty sure the block's spark-plug-slot is damaged/untrue, cannot even drill-in the new spark plug I got when trying to revive this 193t this afternoon....I'm OK with the insertion of a spark plug in a manner where "it'll never come-out again", which is why I was OK trying to drill it in, but still no luck (may try again, after cleaning-up the new spark-plug's threads since they got a lil mashed the 1st attempts) But if I cannot get it to take this spark-plug, what are my options? I really like the 193, used to own a 194 actually, want this saw would pay maybe $100 for re-threading of that slot but no idea where to even go for something like that..

Thanks a ton for any help getting this "Echo-guy" to have a 193t among his climbsaws ;D
[pic of unit, and picS of the spark plug slot, below!]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'm given broken 2-strokes often enough since I'm usually able to fix them if it's not some catastrophic failure (even then, maybe ;D ), anyway I cannot get any info on what happened to this 193t since its donor was not the one who'd thrown it out originally, however it looks pretty much like it was hit by a car that "realized & backed-off" once they hit it, I say this because the 2 damaged areas are "connected" and couldn't have both have been done by a drop (from any height), would've required "squishing" the unit:

- left-handlebar's AV mounting is sharply bent, and:

- air-box's cover was off, which is trivial, however when I came home w/ new spark-plug for it (was none in it when I received it), I couldn't get it to screw-in, and realized the threading in the block's spark-plug slot was off :(

[Different angles, hoping the un-true-ness of it shows, kinda hard to see but it's not really 1 section the whole thing seems slightly warped am surprised old plug was able to be removed:
20210320_122950_HDR.jpg 20210320_123038_HDR.jpg 20210320_125011.jpg 20210320_125031.jpg (right at the top, the first spot where threading starts, is clearly 'un-true' but sadly seems the entire slot is un-true :/ )


I did put my drill on the plug, thinking maybe I'd "force it", still thinking there's a chance I could get that to work but remembered that "re-threading" exists so I just paused everything to come consult w/ you guys! The new spark plug's threading is already rough from me trying to drill it into place (since hand-pressure isn't enough at all), will clean that up before any next-attempts but honestly if there's a way for someone to just "re-thread" the hole for me it'd clearly be worlds better!! I know that's specialist-help, but I like the 19*T series (used to have a 194t actually) so would happily pay up to say $100 for re-tapping of that hole (or maybe I just source the engine block "half" that has it??)

Thanks a TON for any help on this one, I don't need help w/ the airbox itself in fact I always mod them anyways so was kinda looking-forward to making a custom fiberglass 'airbox cover' and installing my own filtration, but can't/won't bother with anything til I know I've seated a plug & gotten it to turn-over (compression feels very high, fuel in it was not stale, have no worries on unit's condition besides the obvious!)

(PS- I should note I am OK with "Installing it permanently", for instance when I was using the drill to try and "force it" into the bad threading, I figured that if that worked I probably wouldn't be able to swap plugs again in the future, that is OK I am fine with the plug being "permanently stuck" if it lets me get this guy running!!)

spark plug's threading, and packaging (I mean, the Stihl computer at Ace Hardware told me it was the right plug, have no reason to doubt :p )
20210320_125109.jpg 20210320_133355.jpg

AAaaaand the bastardized unit itself, I'm pointing at the bad-spot on the handlebar on the left, the metal AV connect is badly bent but still stable (and I'd reinforce it before use anyways, weak/questionable handlebars scare the F outta me!), I'd initially have thought a bad fall could do this since I've heard Stihl's don't take falls like Echo's do, but this thing was squished between the handlebar and the air-box, so badly that the pressure went "past" the airbox and onto the plug's head itself, mangling my plug-hole!
20210320_125241.jpg
(what a cute lil machine, lol, unsure why I love the look of Stihl gear so much :p )
 

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eyehearttrees

Active Member
Location
Tampa-Area
Hmmmm....just looking at the pic here I can see that someone has tried taping it, which makes me think someone DID get a plug in there after the "squish event" lol, fingers-crossed here ;D
 

Jonny

Well-Known Member
Location
Buffalo
I don’t understand, what are you doing with the drill?

Should be able to buy the right size tap that’s made for aluminum threads.

Should go without saying, but the saw needs to be upside down when messing with the threads. Even cleaning up existing threads can cause some metal to fall into the cylinder.
 

eyehearttrees

Active Member
Location
Tampa-Area
I don’t understand, what are you doing with the drill?
Using a 'bit' that's sized for the head of the spark-plug, so I can generate quick&powerful torque that I couldn't generate by-hand (my scrench's are "regular" and this Stihl-spark-plug was a weird dimension I've never used, had to get out the socket-set :p )

So yeah was literally "lining-up" the plug with the hole, I "padded" the deep-socket (so the plug protruded more) so I could get proper pressure on it, then I'd line-up and just slam the trigger, hoping I'd "forcibly alter/move the threading so it'd take, even if it meant it's the last spark-plug that's ever going in/out of that hole, would still do it - but after trying "~75% strength" and getting nothing but gnarled metal on the 1st millimeter of the 1st thread of the spark-plug, am guessing I cannot "force it" here (am also fearful that, if accomplished, the plug may not be "centered"/oriented 100.0% properly and am uncertain how much margin for error there is there, if it's say 0.25mm off-center....or not sunken-in past 90%.....)

Should be able to buy the right size tap that’s made for aluminum threads.
Guessing you mean to say the threads I'm dealing with (spark-plug-hole female threads, a part of the block itself) are aluminum? And that there's a "consumer-grade" product I can buy??? That'd be pretty darn awesome, thought I knew about everything Home Depot had but thought "re-threading" something required metallurgic skills :p

Should go without saying, but the saw needs to be upside down when messing with the threads. Even cleaning up existing threads can cause some metal to fall into the cylinder.
It......it *should*, shouldn't it?!? ROFL!! Had cans of comp'd air (no real compressor here, yet), flashlights, head-mount flashlights, kept blasting the thing & was always aware of piston-position (IE, *NEVER* working-on it when the piston is moving-towards the top, want a 1/10th pull to pull that piston *away* from me!)

But yeah thanks for mentioning, even once I realized I'd left a couple metal-slivers on the "block's female plug-hole" threading, I figured holding it upside-down while blasting-in the comp'd air (with its nozzle inside the jug) was sufficient...will certainly swap to "working upside-down" so anything HAS to fall-from, not *into*, the jug!

Thanks a ton for the reply, was afraid this'd be a >$100 thing (getting that hole "ready for anyone to insert/screw-in a spark plug") and had told myself $100 was my firm limit, parts & equipment/tools/etc, on this project...consider the 193/194t's to be "worth about $200-250 (mine/personal assessment of value, am an "echo guy" lol, returned a 194t once so I could go buy the WAY superior, killer 355t ;D ) so with the mangled AV and "relatively-unknown" state I'd be comfortable going about $100 into this thing!
 

Jehinten

Well-Known Member
Location
Evansville


Something like this may work. Its designed for vehicles, but I suspect in theory it'd work on a chainsaw as well, as long as you get the correct size. I do not know the correct size and only listed this one as a resource.


In past experience I've dealt with cross threaded spark plugs twice before. The first time I was working with my grandpa who took the old spark plug to the bench grinder and put a taper on the end. Carefully screw it back in and it works as a tap to chase the threads. Remove and insert the new plug. I used the same trick on my second occurrence as well, worked great both times. Both were on car engines.

Last option, look into a new cylinder. I've not pulled apart a 193t but a 391, and 661 were both easy rebuilds.


As far as cleaning out bits of metal, take off your muffler and set the piston just below the opening. Blow air through the sparkplug hole to blow contaminants out of the exhaust port.
 

eyehearttrees

Active Member
Location
Tampa-Area
In past experience I've dealt with cross threaded spark plugs twice before. The first time I was working with my grandpa who took the old spark plug to the bench grinder and put a taper on the end. Carefully screw it back in and it works as a tap to chase the threads. Remove and insert the new plug. I used the same trick on my second occurrence as well, worked great both times. Both were on car engines.
Thanks this is precisely what I was hoping for ie a chance to try something else before bringing to my friend who I expect can rethread it for me (well I know he can it's whether he will lol) Because when I'm looking into that hole in the block, the threading seems "evenly-damaged" if that makes sense, I think "chasing the threading" as you say is possible here, but I was running into issue by using a regular plug (instead of altering its tip, like you describe with the grinder, will do that and try again!)

Last option, look into a new cylinder. I've not pulled apart a 193t but a 391, and 661 were both easy rebuilds.
I enjoyed the 193 (well, 194) enough that I think I'd be willing to drop $100-150 to have this guy working...if I go the route of buying new stuff, am I better off buying the parts or simply go to a pawn and find a used 193 to work off of? I figure that way I'd have a parts-saw to pull from, in the future, yknow? Or is there a good enough "stihl parts market" that it's cheap&simple to get the part I need? I'm pretty ignorant of Stihl, I know you can get "stihl clone" stuff but don't know if that's OK to use in a case like this..
 

eyehearttrees

Active Member
Location
Tampa-Area
As far as cleaning out bits of metal, take off your muffler and set the piston just below the opening. Blow air through the sparkplug hole to blow contaminants out of the exhaust port

Great tip thanks, would've been taking the muff off to "open it up" anyways, thanks for mentioning this :)
 

Jehinten

Well-Known Member
Location
Evansville
Thanks this is precisely what I was hoping for ie a chance to try something else before bringing to my friend who I expect can rethread it for me (well I know he can it's whether he will lol) Because when I'm looking into that hole in the block, the threading seems "evenly-damaged" if that makes sense, I think "chasing the threading" as you say is possible here, but I was running into issue by using a regular plug (instead of altering its tip, like you describe with the grinder, will do that and try again!)


I enjoyed the 193 (well, 194) enough that I think I'd be willing to drop $100-150 to have this guy working...if I go the route of buying new stuff, am I better off buying the parts or simply go to a pawn and find a used 193 to work off of? I figure that way I'd have a parts-saw to pull from, in the future, yknow? Or is there a good enough "stihl parts market" that it's cheap&simple to get the part I need? I'm pretty ignorant of Stihl, I know you can get "stihl clone" stuff but don't know if that's OK to use in a case like this..
Use OEM, any stihl dealer can get the parts for you.

If you want to try aftermarket parts, do that on stuff that you won't have to tear down the entire saw to replace when it fails.
 

eyehearttrees

Active Member
Location
Tampa-Area
Use OEM, any stihl dealer can get the parts for you.

If you want to try aftermarket parts, do that on stuff that you won't have to tear down the entire saw to replace when it fails.
Oh I didn't know if there was also a good, legitimate "performance aftermarket scene" for Stihl or if it was just the hutzl/etc crowd (which seems to be case based on how you write that...I'm not a Stihl guy by any stretch it's my only stihl powerhead in fact, but I've had the 194t and enjoyed it for a 'middle-range' climbsaw!)

Will check online for price of the "part of the block" I'd need to replace (what's it called, specifically, so I can be sure I'm looking at just the piece I need?) because if it's $50 I'd be happy/eager to do my first real engine rebuild and I'd order it (wouldn't spend $100 though)

I WISH there were a way to just put JB Weld on it, jam it in-place and consider the saw "works til the spark-plug dies" since it'll be stuck in there :p But my understanding is there's no "epoxy" type product that can hold that heat/pressure/forces of keeping a plug you need a helicoil, what I really worry about is whether *I* could do it I mean the tolerances for alignment/orientation must be pretty damn exacting in that location IE the height of the plug so installing new threads/helicoil - even if I do line it up dead-on - still may fail me...

Gonna see what Ace has for "hole threaders" and see if I can brute-force it, either that or a rebuild if that part of the block is like $50 or under!
 

eyehearttrees

Active Member
Location
Tampa-Area
I'd try installing a helicoil insert.
Have you ever done this? I feel like this could work - and is probably the path a pro would take in fixing it - but I wonder whether I could possibly line-up and orient it just-right (the tolerances for spark plugs, I mean the gaps of plug to electrode and all that make me think it's not going to be forgiving if my plug's electrode is 2mm higher or lower in that hole than OEM-spec!)
Seems only option besides reaming/fighting one in there....my favorite outcome woulda been if I could've just forced-in a plug (even if that meant it was the last plug the saw could ever use) but was using a socket on my impact drill, using spark plugs with vertical/perpendicular slits in them (to act as 'tappers'/threaders) to no luck which makes me think helicoil is only option, but that I'm unqualified to do it..

If I can get an OEM replacement for that edge of the block for a reasonable price I'd try rebuilding it, the airbox already needs rebuilding anyways and was going to use fiberglass for a custom setup so it's already going to be on the table a while (projects like this can linger lol!)
 

Jehinten

Well-Known Member
Location
Evansville
Will check online for price of the "part of the block" I'd need to replace (what's it called, specifically, so I can be sure I'm looking at just the piece I need?)
The cylinder is what you'd be replacing. If it was damaged before going out of use it's possible that metal got in there and could have scarred up the piston as well.

For parts shopping online, and looking at exploded views, I like to look at this site. It's usually one of the first results when I Google a make/model of a saw such as "stihl ms193t parts" on this site your cylinder is no longer available (it will be in stores) but is listed at about $60

 

Dan Cobb

Well-Known Member
Location
Hoover
I have not installed a helicoil insert. When I had a crew of mechanics, they used them from time to time. They were solid mechanics, but not geniuses or machinists. I'd surf YouTube.
 

eyehearttrees

Active Member
Location
Tampa-Area
The cylinder is what you'd be replacing. If it was damaged before going out of use it's possible that metal got in there and could have scarred up the piston as well.
Damn! Not worth it anymore....can't do all this based on "compression feels OK via the 'starter-rope method'", gonna junk it (ie find someone who's got one to re-home, I'd keep for parts but no other stihl gear)

The 193 is an awesome saw but if I'm possibly rebuilding the whole engine, heck I don't even know quality of most of the rest it could be a total dog, not worth it (if it were a 200t...)



That site is brilliant, I had an echo polesaw (ppt266, MSRP $600, received as trash-level goods from prior owner who'd broken its adjustable shaft & tried/failed to fix it themselves), I probably blew over $100 and god-knows how many hours but rebuilt it & to this day it is a beast of a saw for 25cc. ^That site was requisite there would've been no way and I had both of the Echo technical manuals as well. That site rules and also seems to have every saw in existence, would be the homepage on my mobile browser if I left data on ;D (errr no actually it'd probably be my control panel here....which is why I don't keep my Data on on my phone!)
 

eyehearttrees

Active Member
Location
Tampa-Area
I have not installed a helicoil insert. When I had a crew of mechanics, they used them from time to time. They were solid mechanics, but not geniuses or machinists. I'd surf YouTube.
Thanks, am aiming to try one last "jam a plug in" attempt, before finding this guy a new home (actually think I can steal its bar, it is a 3/8" and stihl bars are supposed to be so good plus just put a chip in my 14" echo pro bar, which was supposed to be my nicest bar yet it's only one I've ever put a crack in ever!)
 

Jonny

Well-Known Member
Location
Buffalo
Did you try cleaning the threads with a tap yet? You can do it with a more common tap made for steel threads, just be careful, don’t turn really hard. This might be a really simple fix to get your saw going.
If it’s anything like the 192T, it’s a really good top handle saw. Not spectacular or made for racing, but my 192T has been very reliable.
 

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