Stihl 039 has stripped bar stud - how to fix it?

[oldmar]

Many times when I am having trouble taking advice, it is because I lack the magic ingredient.

I had some trouble understanding transistors, and how they amplify a signal, until someone explained to me that the transistor, when tickled with a small AC signal, makes a bigger COPY of that signal using high voltage DC. Simple, no? It is, unless you lack the magic ingredient, which was for me, the word COPY.

In this case, I think that the magic ingredient is the understanding of where the thread (on the chainsaw, not Arboristsite) has failed. I should probably say "on which component the thread has failed". While it is possible that the bar nut is stripped and the stud remains undamaged, it is highly unlikely. You would have to cut the nut off carefully in order to find out, and what you'll almost certainly find is that the stud is boogered as well.

So if we accept that the stud is lunched, it doesn't much matter how we treat it, we just need it out. I vote vise grips and counterclockwise rotation. Remember that vise grips (and channellocks) work when you're pushing on the fixed handle. If you are holding the tool so that the fixed handle is cradled in your palm, (snicker) and the moveable handle is being squeezed by your fingers, (snicker) you should be pushing the tool, not pulling. (Snicker snort) Used in this manner, the tool tends to tighten on the fastener, rather than loosen.

Threadkiller has spoken.

 

[donjr5]

The best stud remover I've found is the vice grips.
To install, I used to double nut using a bar nut and a jamb nut. 3 months ago I discovered a better way: take an 8 mm coupling nut (it's about 7/8" or 1" long). Counter bore it with a 3/8 drill bit about 1/2" deep. It will thread onto the stud, clear the shoulder of the stud and stop against the raised ring on the stud. It gives lots of thread engagement, but turns back off the stud without backing the stud out. Works just like Stihl's $12 tool made for the purpose.
Use a bit of locktite on that rear stud, if it loosens up, you'll mess up the ignition module and possibly mess up the oil pump connector.


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[kevin j]

ake an 8 mm coupling nut (it's about 7/8" or 1" long




or a short piece of tubing onto the stud, then the bar nut.

 

[thaugen]

Thanks to all who replied

Even the sarcastic replies. I expect to find stripped threads on the stud when I remove the nut (assuming I can pull/lever it off the stud. I'll be patient and not fire up the heat wrench unless all else fails. - magnesium!)

Speaking of heat, earlier another poster wrote this about studs: "Then I heated up the bar stud with my propane brazing torch (like you use to sweat copper pipe). The repair manual says to heat it up to remove it, I assume to soften the thread adhesive. So I did this for 10 or 15 seconds or so."

If the factory used thread locker I assume the heat treatment would ease things a little when using the Vice-Grips by applying force on the stationary handle.

BTW, on an 039 is the rear stud not only an engine mount but also screws into the oil tank (so I'll need to drain it first)?

 

[oldmar]

If the factory used thread locker I assume the heat treatment would ease things a little when using the Vice-Grips by applying force on the stationary handle.

BTW, on an 039 is the rear stud not only an engine mount but also screws into the oil tank (so I'll need to drain it first)?

Heat should help to deactivate threadlocker. If you heat the stud gently, allowing the surrounding case to heat (gently) as well, and then quickly cool the stud with an ice cube or a shot of carb cleaner, it should back right out very easily. I only mention the thing about the vise grips because most people think that they work equally well in both directions, they do not.

You only need to drain the oil tank if you're working on the saw upside down. If the case threads were stripped, and bits of metal were falling in thorough the stud hole, then yes, drain, clean and refill. If the oil tank is less than totally full, you should be Ok.

 

[sefh3]

The engine housing is plastic. I would not use heat at all. Use a pair of vise grips and remove it. Look in my signature line. I have a few thread that give great detail on how to assemble and disassemble this saw. Stay far away from heat!!!!!

 

[Fish]

Sorry, didn't have an 039 to tear down to take a pic of me pinch the rear bar stud in a vice and rotate the saw counter-clockwise,
but here is a pic of the bar stud removed.

 

[Fish]

I use the bench vise because it is the easiest way, and does less damage than vice grips. An expensive stud puller works best, but it still
mars the stud a little, so I don't bother trying to resell them.

 

[thaugen]

Thanks to all who replied

With your advice I feel confident I can replace this stud.

Tom

 

[Fish]

Stihl puts a generous amount of blue loctite on them, you might go back with a dab as well, so you wont bring the stud instead of the nut when taking the bar off.

 

[thaugen]

Got the stud out

The oil feed stopped up so I had to dismantle the saw. No luck pulling and twisting the nut - it was captive due to the bunged threads. So a 4 1/2" angle grinder with a cutting wheel made the notch you see in the photo. I stopped when the wheel just started to nick the cover, not quite all the way through the nut. Then I turned the nut 180 degrees and sliced the other side with the cutting wheel. Then I used an old-fashioned lug wrench - the type with a chisel end to pry off hubcaps, and jammed it into the nut and the nut unscrewed! I had been planning to bust the nut in half but there was no need as the nut rose on the threads.

After removing the nut the stud was still warm so the Vice-grips made short work of removing it. A new stud, nut, chain and sprocket and I should be back in business. This saw was a stone bargain ($11 after some horsetrading) and I have more time than money, so the hassle of changing the stud is worth it.

Thanks again for the advice, Tom

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