Would you repair an Exhaust Stud With JB Weld?

[rxe]

I have a Stihl 07 that is verging on a parts saw, but I am trying to persuade myself to save it. OK, I don't need that much persuading.

One of the biggest problems with this saw is the exhaust. The previous owner (or maybe the one before that) grafted a TS-350 exhaust onto it, totally mullering one of the exhaust studs by screwing something of a completely different thread into the cylinder. They also managed to crack the casting slightly around the stud hole. If I screw a length of stud in, it will hold, but only just - if I put any tension on it, it would fail.

I could helicoil or timesert it - but as the casting is cracked, I think the insert would probably pull out after a while.

I am thinking of cutting a length of M6 stud to suit, filling the hole up with JB Weld, and screwing the stud in. My big worry is the temperature - JB Weld is good to 500F - and I have no idea how hot that stud mounting will get. I've googled and found 2-stroke aero-engine cylinder head temperature gauges that only go as far as 500F...which seems promising.

Anyone done this? Did it melt?

 

[Mike Van]

I think the JB's worth a try, it's a pretty cheap fix if it works. I've fixed a cracked block, a leaking hydraulic tank & a few gas tanks with the stuff, all are still in use today. I don't think I'd fill the hole though, you may find that not enough can squeeze out as you screw the rod in. It might act like a pressure thing, and force the split/crack open even more. I'd just coat the threads & try that.

 

[ScottWojo]

Weld it.

Some shops can do a fine job of welding the crack to reinforce it. Or weld the whole thing up and redrill the hole. Find a truck place that does magnesium and aluminum welding.
Do the back door thing. Go in the back door and say "howdy neighbor, I work just down there at the (insert name here)"
Tell them you always wanted to stop in and an indroduce yourself. Take em a box of donuts and coffee in the morning.

"Oh wow you guys do magnesium welding? Thats so weird, I have a stupid little welding job in the back of my (truck, car, or bicycle) You think you can handle such a huge job?"

After the do the job take the cylinder to a machine shop the next day and repeat. Have them mill the welds down and drill and tap the whole.

Tell all these guys if you ever need and discount beer that you work just down the street at the beer distributor. "Make sure you ask for (insert name here), I pretty much run the place. Just come in the back door."


There is a great hidden economy through the back door of every place. Donuts and beer are the currency.

Love these tips? Keep feeding me rep.

Scott.

 

[timberwolf]

Screwing the stud in with a coating of JB may work, one problem to watch out for is if the end of the hole is closed, you will have some hydrolic problems working against you. If the back end of the bolt hole can be vented it will work better. Don't put any force on it till it's set up and it should have a chance.

I have even used JB right in the exhaust flange on a piped alky saw and it has held up, but I wouldn't expect it would on a daily used work saw.

 

[ccfr63]

I've used JB Weld on muffler studs several times on trimmers and chainsaws and it always works. Just try to force some of the JB into the crack and then some around the threads of the screw that you are going to use, screw it in the stud, and then, if possible put a pair of needle-nose vise grips on the stud and leave it all alone until it sets up real well. Like I said I've done this several times and it has worked well for me and hasn't failed yet.

 

[Lakeside53]

I would drill/tap it out and put in the correct size steel TIMESERT insert with red loctite. The crack won't matter when the insert is in place. If the hole is too big, drill it out, tap it with any coarse thread, make an aluminum 6061 plug with the same thread, insert with red loctite, then drill out and retap to orginal. Sounds like a lot of work, but it's not really.. maybe an hour or two of messing around...

500F with JB.. well.. they may claim that, but above 300F or so it's getting soft, and at 500F it will fail completely - not melt, but fail chemically.

 

[tomdcoker]

Would you repair an Exhaust Stud with JB Weld.

I know what a helicoil is. I have used some in my shop, but what is a timesert.. Tom

 

[ScottWojo]

It is something that will make you throw all those helicoils away.

Some of the inserts have a pin that slides down into ther material locking it into place. You thread it in with lock tite and hit the pin in with a hammer.

Google is your freind. Throw those helicoils away.

 

[49KB-2]

I know what a helicoil is. I have used some in my shop, but what is a timesert.. Tom

http://www.timesert.com/

 

[Lakeside53]

I know what a helicoil is. I have used some in my shop, but what is a timesert.. Tom

Helicoils are worthless in small sizes. Not much better in larger either.

A timesert is a thinwall synchronised thread soild body insert. Originally created to make OEM approved repairs to helicopters. Hard to find, but there are a few places on-line to get the kit.

The repair is permanent and often better then the orginal.

 

[bowtechmadman]

I used JB weld to hold a spark plug into an old Isuzu trooper...helicoil had failed. Lasted over 20,000miles till I unloaded it.

 

[rxe]

Thanks for all the responses....

Here's what I'm going to do.

1) I'm going to try the JB Weld first - as several have said, it is a cheap fix, and might just work. It isn't a work saw, so it might work for a while. If it fails, I haven't damaged anything by using it. The stud hole is open at the back, so I'm not worried about hydraulic problems as I screw the stud in. If I have time over Christmas I may hook up a thermocouple to another 07 I have, do some cutting and see how hot it gets.

2) I will also order some Timeserts - this isn't the only thread that someone has ruined, they seem to have replaced many of the starter bolts with M7 or M8 items. It would also be a good project to learn how to use Timeserts on. The only problem with Timeserts is that I will have to deal with their distributor in the UK (Wurth) which will be a world of pain.

Lakeside...my definition of "slight" crack may not be the same as yours - do you think a Timesert would hold in this?

If not, then I will be following the Wojo path to goodness via the doughnut shop!

 

[belgian]

judging from the pic, I think welding will be the only option here if you would like a permanent solution. The outer part looks as if it can break off any time.

I have used JB weld on a muffler stud for a dolmar CX and it did hold for a test run. This is not a worksaw either, so you just might give it a try.

 

[ScottWojo]

oh ok then...

I DO NOT APPROVE. but...take a hammer and bust the rest of that ear off. If you can get a nut behind the ear and use it as reinforcement better. Clean every thing till it shines, and rough it up with sandpaper or coarse wire. Then surround the nut, stud and where the cracked ear was with the JB weld. You can use wax paper against the JB for a smooth finish when your done.

Make sure you tell anyone who buys the saw that its "there."


Scott,

 

[rxe]

Make sure you tell anyone who buys the saw that its "there."

Don't worry, I'm not planning on selling it - it would be a very strange way of making money given the hours I'm going to put into it. No, this is about bloody mindedness and learning new skills, rather than profit.

The ear looks awful from the front, but is held on quite well as the fins form part of the back of it. However, I have changed my mind after about 1/2 an hour of surfing. There is a welding rod called HTS-2000 which is claimed to weld aluminium with a propane torch (I have oxy), so I will try and learn a new skill. I will fix up the ear, and fill the hole with weld. Once I have done that, I will put a timesert in, and hopefully that will be the end of the matter.

Yes, it would be a lot cheaper to buy a NOS cylinder than some rods and a timesert kit - but that's not the point!

 

[Stihl 041S]

There are other inserts,epoxy beads on the outside that mix when you screw them in,slot in the top and hard as the hubs of he"" . Can't remember the name but great under all conditions.

 

[Lakeside53]

Those are "keenserts" and tend to have a very large exterior - typcal hole size for small threads is 5/16 drill and 3/8-18 tap. I beleive the outer coating is just loctite, and not high temperature. I use them now and then but only for holes that are bady slogged out. Often there isn't enough "meat" around the hole to use one.

 

[ScottWojo]

I know those rods very well. I can not remmeber but it seems a company in Fla hat them. it will work well, However, I have never used it for this purpose.

Don't worry, I'm not planning on selling it - it would be a very strange way of making money given the hours I'm going to put into it. No, this is about bloody mindedness and learning new skills, rather than profit.

The ear looks awful from the front, but is held on quite well as the fins form part of the back of it. However, I have changed my mind after about 1/2 an hour of surfing. There is a welding rod called HTS-2000 which is claimed to weld aluminium with a propane torch (I have oxy), so I will try and learn a new skill. I will fix up the ear, and fill the hole with weld. Once I have done that, I will put a timesert in, and hopefully that will be the end of the matter.

Yes, it would be a lot cheaper to buy a NOS cylinder than some rods and a timesert kit - but that's not the point!

 

[Lakeside53]

Thanks for all the responses....

Here's what I'm going to do.

1) I'm going to try the JB Weld first - as several have said, it is a cheap fix, and might just work. It isn't a work saw, so it might work for a while. If it fails, I haven't damaged anything by using it. The stud hole is open at the back, so I'm not worried about hydraulic problems as I screw the stud in. If I have time over Christmas I may hook up a thermocouple to another 07 I have, do some cutting and see how hot it gets.

2) I will also order some Timeserts - this isn't the only thread that someone has ruined, they seem to have replaced many of the starter bolts with M7 or M8 items. It would also be a good project to learn how to use Timeserts on. The only problem with Timeserts is that I will have to deal with their distributor in the UK (Wurth) which will be a world of pain.

Lakeside...my definition of "slight" crack may not be the same as yours - do you think a Timesert would hold in this?

If not, then I will be following the Wojo path to goodness via the doughnut shop!

In this case... welding is best.

If you want to weld it, take of the cylinder first, and grind it back to very clean metal...

You could use HRT2000 "solder" with propane - very tough and stronger than aluminum.

Timesert - well.. depends... but that is TWO cracks.... . You need to drill two or more tiny holes though the cracked portion and PIN them into the base material.

The problem with JB weld is the heat is that is connected back down the steel studs... and these rods pass though the muffler - very very hot.

 

[Dan Forsh]

Don't worry, I'm not planning on selling it - it would be a very strange way of making money given the hours I'm going to put into it. No, this is about bloody mindedness and learning new skills, rather than profit.

The ear looks awful from the front, but is held on quite well as the fins form part of the back of it. However, I have changed my mind after about 1/2 an hour of surfing. There is a welding rod called HTS-2000 which is claimed to weld aluminium with a propane torch (I have oxy), so I will try and learn a new skill. I will fix up the ear, and fill the hole with weld. Once I have done that, I will put a timesert in, and hopefully that will be the end of the matter.

Yes, it would be a lot cheaper to buy a NOS cylinder than some rods and a timesert kit - but that's not the point!

I've tried these too.

I didn't do the work myself but got our fitter at work to do it for me. Both threads had been screwed up on an otherwise good cylinder by the previous fool of an owner. Looked like he'd sheared off the bolts, then tried to drill them out, resulting in another hole being drilled along side them and topped this off with a generous filling of some kind of epoxy crap.

Our guy drilled them both out, filled them with the low temp rods and milled the face back to original. When he did it you could hardly see where the repairs where.

Unfortunately they only held up for a couple months and broke away as you can see in the pictures. The slug of weld you see at the back of the hole rattles back and to.