JB Weld removal ;)

I have used JB Weld for many years on a wide variety of applications and it's never let me down. BUT one thing I have never done is tried to break it loose.

A few months ago I JB'd some velocity stacks to a pair of concentric. Yeah, yeah, seemed like a good idea at the time. Now I want to remove the stacks.

Anybody have any actual experience with this sort of thing?

Nope. It's tough stuff. I'd probably go at it with a propane torch and see if it softens up.

Yes heat will soften epoxy to point where it can be worked off items with putty knife etc.

haha good ol' JB Weld I broke my metal-framed eyeglasses last week and prior to going to eye doc to get new ones 'fixed' the broken pair with JB...still holding great after a week..hopefully new ones arriving soon as the grey gob is a rather jarring fashion statement.....JB Weld the miracle stuff sorry fo de 'hijack'

Heat gun it. I do love the stuff though so save the bits and mail it to me.

MexicoMike said:

I have used JB Weld for many years on a wide variety of applications and it's never let me down. BUT one thing I have never done is tried to break it loose.

A few months ago I JB'd some velocity stacks to a pair of concentric. Yeah, yeah, seemed like a good idea at the time. Now I want to remove the stacks.

Anybody have any actual experience with this sort of thing?

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my only experience with that sort of thing was destructive in nature. don't think you want to do that....

maylar said:

Nope. It's tough stuff. I'd probably go at it with a propane torch and see if it softens up.

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What's the melt point of Amal carburetors?

cyclegeezer said:

What's the melt point of Amal carburetors?

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Well below that of softening of epoxy....not a problem for this situation.
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***EDIT: Opps, I meant the epoxy will soften well below melting of the carb metal....

Tornado said:

Well below that of softening of epoxy....not a problem for this situation.

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Pot metal with a propane torch... hmmm. Thinking of Liquid Metal Man now but he recovers every time.

Yeah, I was thinking heat but concerned about the carb material. I'm thinking I'll try a propane torch, trying to keep the heat directed onto the AL Velocity stack and hope it will break loose without as much heat transferring to the carbs. Then try to work the stuff out of the threads on the carb bodies. Might be a lot less trouble to just buy another set of premiers and have a "velocity stack" pair and a Ham Can pair!

I DO like the performance with the stacks but the no-filter thing just keeps nagging at me...

Regardless of brand, the majority of consumer purchased room temperature-cure epoxy is just a firm rubber at 200F, which should allow removal with a bit of force. To avoid overheating and damaging the carb I’d soak the carb in boiling water which will easily get you above the glass transition temperature of the epoxy, without damaging the carb, where the epoxy will be in the rubbery state and you can begin messaging it for removal.

I hope the above doesn't shock too many people, as we are used to witnessing the impressive structural strength of cured epoxy at room temperature, where it is in the glassy state and can be a very tough strong material. However, upon heating, RT-cure epoxy weakens quickly as it transitions to the rubbery state where the strength decreases dramatically. To get into the high temp performance end of epoxy technology, the cure temperature typically moves way up, requiring perhaps 250F and greater cure temp, as found in the aerospace and electronics industry. Such epoxy materials exhibit dramatically higher temperature performance than their RT-cure analogs.

If you care to experimentally find the temp at which the epoxy transitions from glassy to rubbery you can coat out a long thin strip (1/32 to 1/16” thick) of your favorite epoxy on wax paper so it can be released from the paper after curing. After RT-cure you may want to push it to full cure by heating at perhaps 160F (70C) for an additional hour. You can then submerse in water baths (or place in temp controlled oven) of increasing temp and withdraw for examination to determine where your stiff rigid strip of epoxy becomes a limp piece of rubber.

Well then , it shouldn't take much heat (relatively speaking) from the torch on the AL velocity stack to do the job! I'll let you know!

MexicoMike said:

Well then , it shouldn't take much heat (relatively speaking) from the torch on the AL velocity stack to do the job! I'll let you know!

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Do try a heat gun frst....I speak as someone who has melted aluminium with a propane torch, unintentionally!

Yes, I held the heat on it too long, but just be aware that can happen.

Equally I have used JB weld inside a Norton motor and it can hold at very high temp, but I have used it to plug holes where there is no one trying to separate anything, so I also think it will go to a state that will allow separation without necessarily meaning it will fail in use.

On my VM36s I have just used an ordinary epoxy to hold the bellmouths, heat gun is certainly enough there for removal, which I have done a couple times to change air jets.

Sorry to hijack the thread, but did you use the JB weld to fill the void between the velocity stack and the carb inlet? I have a set which I want to fit and I was wondering about that...

Yes, I applied the jb weld to the threaded area of the carb inlet and then placed the stack onto it, wiping off any excess JB that oozed out anywhere. Looks great- like the stacks were machined onto the carb!

Wondering why you wouldn't use something less strong here, like a decent automotive silicon or polyuerthane sealant? Would hold pretty well and be removable later.

Tornado said:

Wondering why you wouldn't use something less strong here, like a decent automotive silicon or polyuerthane sealant? Would hold pretty well and be removable later.

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I'm wondering exactly the same thing; I had both of those products on hand...

MexicoMike said:

I'm wondering exactly the same thing; I had both of those products on hand...

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Oh well...live and learn, Eh?

BTW, I thought you were really happy with the VS's. Did the grit & grime worries get to you? Whaddabout some kind of mesh/light filtering within the stacks to keep out the bigger stuff?

It's totally the lack of air filtering that's bothering me. The stacks work great; the bike runs noticeably stronger. But it's quite dusty here and although I thought originally I would just accept that and refresh the engine as needed, I just can't get my head around intentionally causing engine wear.

SAWZALL.