Decompression valve thread repair

[StihlEchoingHusky]

I stripped the internal threads to the decompression valve on a saw. And Just out of curiosity has anyone ever tried just filling the *f-worder up via Tig or mig?? Or would the heat/spatter cause problems with the nikasil? Btw I have no clue if there is spatter when welding aluminum.ive only welded iron and steel

 

[kanscruzer]

how about tapping it out to 1/4"pipe & put a plug in it ,,,,,, you can even get plug in aluminum

 

[srcarr52]

Just use an M10x1.0 heli-coil. The small thread pitch makes for a very small wire of the heli-coil so it all hides behind the sealing crush washer.

 

[dangerousatom]

If ur thinking of tigging it and you have the odds n ends laying about. Weld a 1/2” or bigger ball bearing (larger then the hole diameter) to a bolt that’s longer/deeper than the cylinder. Weld that standing up on the bench and put the cylinder over it to “plug” the decomp hole from the bottom. That will keep any slag or drips from getting into the cylinder. I will say any cylinder I’ve ever welded acts like it’s super soft and evaporates faster then you can get a read on what you need to do to get it right.

Spitballing here……I have not tried it yet but if u don’t have a Tig ….IMO if u want to plug it with aluminum, maybe do the above method with a piece of wood, but melt down one of those aluminum filler rods and pour it in all in one shot. Use a bit of broom handle or soft-ish wood to make a domed plug. If you put some pressure on the cylinder or bolt it down so that it really compresses up into the hole from inside you shouldn’t get any leak through. It’s the same idea as copper spooning a spot weld on auto body. Experience tells me, be sure the wood is dry or steam will bubble n maybe give u a leak/bad bond.

Otherwise if its a small spark plug size just retap it to the next size up n plug it with a dab of high temp sealer

 

[StihlEchoingHusky]

If ur thinking of tigging it and you have the odds n ends laying about. Weld a 1/2” or bigger ball bearing (larger then the hole diameter) to a bolt that’s longer/deeper than the cylinder. Weld that standing up on the bench and put the cylinder over it to “plug” the decomp hole from the bottom. That will keep any slag or drips from getting into the cylinder. I will say any cylinder I’ve ever welded acts like it’s super soft and evaporates faster then you can get a read on what you need to do to get it right.

Spitballing here……I have not tried it yet but if u don’t have a Tig ….IMO if u want to plug it with aluminum, maybe do the above method with a piece of wood, but melt down one of those aluminum filler rods and pour it in all in one shot. Use a bit of broom handle or soft-ish wood to make a domed plug. If you put some pressure on the cylinder or bolt it down so that it really compresses up into the hole from inside you shouldn’t get any leak through. It’s the same idea as copper spooning a spot weld on auto body. Experience tells me, be sure the wood is dry or steam will bubble n maybe give u a leak/bad bond.

Otherwise if its a small spark plug size just retap it to the next size up n plug it with a dab of high temp sealer

So first thing I need to do is, master licking my elbow since there seems to be a bit more luck involved!

 

[dangerousatom]

Correct…. it is certainly a skilled and difficult task to tig or weld such a small bit if aluminum without error.

 

[StihlEchoingHusky]

Correct…. it is certainly a skilled and difficult task to tig or weld such a small bit if aluminum without error.

I kind of figured as much. From what I heard welding aluminum in general takes a good amount off skill as it is.

I've got a question I don't know if you would know this or not. But I didn't want to start another thread. Is this a legit place?

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[StihlEchoingHusky]

how about tapping it out to 1/4"pipe & put a plug in it ,,,,,, you can even get plug in aluminum

Say if I were to do that would Moto seal used as a "pipe dope" work? Like done with Husqvarna oil pump bolts. I really like this idea. I feel as if the taper would hold it's seal for longer.

 

[dangerousatom]

If you use a taper tap like NPT you don’t need any sealer as long as it seats. Another member and I above mentioned using a larger decomp plug because it has a built in crush washer witch will sealer up

 

[StihlEchoingHusky]

mentioned using a larger decomp plug because it has a built in crush washer witch will sealer up

You wouldn't happen to know what that size would be? It's an 1128 series saw

 

[IH1972]

I stripped the internal threads to the decompression valve on a saw.

What size are the threads that you're trying to fix?

 

[Ace4059]

Could you add a decomp valve delete kit and then silver solder it into place?

 

[800storm]

You wouldn't happen to know what that size would be? It's an 1128 series saw

The Threads are M10-1.0

 

[srcarr52]

If ur thinking of tigging it and you have the odds n ends laying about. Weld a 1/2” or bigger ball bearing (larger then the hole diameter) to a bolt that’s longer/deeper than the cylinder. Weld that standing up on the bench and put the cylinder over it to “plug” the decomp hole from the bottom. That will keep any slag or drips from getting into the cylinder. I will say any cylinder I’ve ever welded acts like it’s super soft and evaporates faster then you can get a read on what you need to do to get it right.

Spitballing here……I have not tried it yet but if u don’t have a Tig ….IMO if u want to plug it with aluminum, maybe do the above method with a piece of wood, but melt down one of those aluminum filler rods and pour it in all in one shot. Use a bit of broom handle or soft-ish wood to make a domed plug. If you put some pressure on the cylinder or bolt it down so that it really compresses up into the hole from inside you shouldn’t get any leak through. It’s the same idea as copper spooning a spot weld on auto body. Experience tells me, be sure the wood is dry or steam will bubble n maybe give u a leak/bad bond.

Otherwise if its a small spark plug size just retap it to the next size up n plug it with a dab of high temp sealer

Just make a sheet metal slip to go in the bore and protect the plating. Then you can weld from both sides if you have to.

 

[Catbuster]

I’ve not had much luck TIG welding cast aluminum… I can’t imagine trying to do it with a wire process. It seems kinda gummy and then a little too much amperage makes it run away into a fluid mess all of a sudden.

If I was going to try, I would probably try to plug it from the bottom, it’ll do two things-protect the inside of the cylinder and act as a heat sink.

1128s aren’t that hard to pull over, at least stock. You could drill and tap NPT and stick a plug in it. Aluminum is an option, as is brass, or stainless.

If you want to repair it, as others have said, run an M10-1 helicoil. It’s probably the easiest route to take.

 

[StihlEchoingHusky]

I’ve not had much luck TIG welding cast aluminum… I can’t imagine trying to do it with a wire process. It seems kinda gummy and then a little too much amperage makes it run away into a fluid mess all of a sudden.

If I was going to try, I would probably try to plug it from the bottom, it’ll do two things-protect the inside of the cylinder and act as a heat sink.

1128s aren’t that hard to pull over, at least stock. You could drill and tap NPT and stick a plug in it. Aluminum is an option, as is brass, or stainless.

If you want to repair it, as others have said, run an M10-1 helicoil. It’s probably the easiest route to take.

The helicoil in the combustion chamber of a engine just doesn't sit right with me. I know countless people have done it with spark plugs. But that doesn't take the fear of it coming out and into the engine away from me. Im probably Gonna just tap it to the next size up or 1/4npt. I've got a ton of npt taps and manual Ridgid die set. (Although dies wouldn't be needed) I'm thinking I'll probably go with naval brass.

 

[srcarr52]

I’ve not had much luck TIG welding cast aluminum… I can’t imagine trying to do it with a wire process. It seems kinda gummy and then a little too much amperage makes it run away into a fluid mess all of a sudden.

If I was going to try, I would probably try to plug it from the bottom, it’ll do two things-protect the inside of the cylinder and act as a heat sink.

1128s aren’t that hard to pull over, at least stock. You could drill and tap NPT and stick a plug in it. Aluminum is an option, as is brass, or stainless.

If you want to repair it, as others have said, run an M10-1 helicoil. It’s probably the easiest route to take.

You need more gas coverage or you need to clean it better. Aluminum will get an oxide layer that melts at a much higher temperature than the base metal. So you'll have a skin that makes it look like it's not molten but the metal under it is and as soon as you break the skin it all falls away.

 

[davidwyby]

The helicoil in the combustion chamber of an engine just doesn't sit right with me. I know countless people have done it with spark plugs. But that doesn't take the fear of it coming out and into the engine away from me. Im probably Gonna just tap it to the next size up or 1/4npt. I've got a ton of npt taps and manual Ridgid die set. (Although dies wouldn't be needed) I'm thinking I'll probably go with naval brass.

I need to do my 395.

The port into the chamber should be a lot
Smaller than the helicoil, meaning the helicoil can’t get in there, also meaning you need a bottom tap. I despise helicoils. We replace them regularly after failure, they are fiddly, expensive and require special taps.

I prefer solid one piece time serts. The one I have for my 395 is std 9/16” thread on the outside.

 

[stihl livin]

The helicoil in the combustion chamber of an engine just doesn't sit right with me. I know countless people have done it with spark plugs. But that doesn't take the fear of it coming out and into the engine away from me. Im probably Gonna just tap it to the next size up or 1/4npt. I've got a ton of npt taps and manual Ridgid die set. (Although dies wouldn't be needed) I'm thinking I'll probably go with naval brass.

If Shaun recommends a helicoil I’d trust him. The guy knows his stuff.