JB Weld removal ;)

[Chuck_Wagon]

JB weld website says 600 degrees will soften it up.

 

[MexicoMike]

Thanks, If that's the case, the stacks are going to stay where they are. I'm not comfortable with the carbs getting to 600F. I'll try "mild" heat, monitoring with an IR temperature gun, up to the 250-300 range and see if it turns rubbery as WZ indicated in post 11. I'm concerned that heat much beyond that range could permanently warp the carb bodies and cause the slides to stick. Maybe putting the stripped-down carb in the oven would be better than using a torch/heat gun since the heat would be evenly spread through the entire assembly...

 

[SteveA]

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.

What about some type of 'sock' foam filter over the bellmouths!

 

[MexicoMike]

I suppose that's a possibility I should at least try. Years ago, using a flow bench, we found that a screen as is typically found on a screened velocity stack had about 30% less flow capacity compared to the same stack without a screen. Makes sense, of course, since the screen wire essentially reduces the area of the opening. Since a sock filter has much more filter area than a screen in a stack, it might provide decent filtering without reducing the airflow.

Of course, it may be that the 30% reduction wouldn't matter on a stock Norton engine. IOW, if the motor only requires, say, 60% of what the open stack can deliver, reducing the stack's capability by 30% wouldn't matter.

 

[Craig]

Mike , I use a Uni-filter on my VM-34 , used on dirt bikes I think , it has 2 layers of filter sponge over spring the black inner is finer than red outer sleeve , seems to flow well and keeps the grit out ... should not be too difficult to fit similar on a stack

 

[MexicoMike]

Thanks Craig, I'll look into that!

 

[MexicoMike]

FWIW, 300F per the oven temperature setting had no effect on the JB Weld. So since I'm not willing to go to the 600F that JB Weld says is needed, I'll be trying the filters Craig suggested. OR, I guess I could just suck it up and deal with no filters as I originally planned.

Note too self: next time DON'T use JB Weld to attach velocity stacks!

 

[lcrken]

I wouldn't worry that much about the sock filters affecting air flow. 25 years or so ago I was running a Ron Wood Rotax-powered road racer with twin carb head, and used foam sock filters on the carbs. I used them dry, not oiled, mostly just wanting to keep out the larger stuff. On the way to Daytona one year, I stopped at Phil Darcy's shop in Texas for some dyno tuning. After working on jetting and cam timing, Phil suggested pulling the air filters, expecting to see a horsepower increase. We did so, and to his surprise, there was no change in horsepower.

Ken

 

[Craig]

When I switched from K&N pancake to the Uni , think I remember having to adjust carb as better air flow through the foam Uni .... was a while ago and haven’t had a reason to look since ....

 

[WZ507]

FWIW, 300F per the oven temperature setting had no effect on the JB Weld. So since I'm not willing to go to the 600F that JB Weld says is needed, I'll be trying the filters Craig suggested. OR, I guess I could just suck it up and deal with no filters as I originally planned.

Note too self: next time DON'T use JB Weld to attach velocity stacks!

You accomplished all that can be accomplished with the 300F excursion. You had the epoxy in the rubbery state and it still had too much strength to remove, which isn’t at all surprising as it would not require much strength on a thread of that size to keep you from rotating the threaded parts. Remember that the rubbery state encompasses materials that range in modulus from very soft and compliant medical elastomers to highly elastic and tough tubing, to tire rubber, to Bobcat treads. Think of your undertaking as vulcanizing a liquid rubber in the threaded joint, and how nearly impossible it might be to separate the joint after the fact. As you've noted, you obviously require a very low modulus rubber adhesive the next time around if you intend to separate the parts in the future.

Because the epoxy is a x-linked polymer it will never melt or flow, so increasing the temperature above 200F would have only minimal effect on the rubbery modulus. The suggestion of going to 600F refers to the upper temperature excursion the epoxy can tolerate for 10 minutes (from the TDS link below) before it will degrade. At 600F continuous exposure the polymer will char, decompose and simply go away, as will almost all organic polymers (consider what organic materials spilled in your oven look like over time at high temperature and the grey dust remaining after a thermal cleaning cycle in your oven).

http://www.aeroelectric.com/Mfgr_Data/JB_Weld/JB-Weld-Technical-Datasheet.pdf

 

[baz]

You accomplished all that can be accomplished with the 300F excursion. You had the epoxy in the rubbery state and it still had too much strength to remove, which isn’t at all surprising as it would not require much strength on a thread of that size to keep you from rotating the threaded parts. Remember that the rubbery state encompasses materials that range in modulus from very soft and compliant medical elastomers to highly elastic and tough tubing, to tire rubber, to Bobcat treads. Think of your undertaking as vulcanizing a liquid rubber in the threaded joint, and how nearly impossible it might be to separate the joint after the fact. As you've noted, you obviously require a very low modulus rubber adhesive the next time around if you intend to separate the parts in the future.

Because the epoxy is a x-linked polymer it will never melt or flow, so increasing the temperature above 200F would have only minimal effect on the rubbery modulus. The suggestion of going to 600F refers to the upper temperature excursion the epoxy can tolerate for 10 minutes (from the TDS link below) before it will degrade. At 600F continuous exposure the polymer will char, decompose and simply go away, as will almost all organic polymers (consider what organic materials spilled in your oven look like over time at high temperature and the grey dust remaining after a thermal cleaning cycle in your oven).

http://www.aeroelectric.com/Mfgr_Data/JB_Weld/JB-Weld-Technical-Datasheet.pdf

Blimey I've never learnt so much from a pair of glued on bell mouths!
Brilliant stuff
Eat ya hearts out all you single mikuni users !

 

[Tornado]

Trying to think of another method...using a solvent to degrade epoxy. Some of the types used for dealing with petrol tank coatings should work...but effectiveness will come down to how much can reach the epoxy along the threading area.

Could also consider chopping off the stacks with a grinder and then using careful application of a dremel cutting wheel getting remaining threaded section out....

 

[MichaelB]

I've been watching this with interest as my introduction to JB Weld was back in the 80's.
Had the heads off of a SBF for a valve job. Machine shop called and informed me we had cracked rocker boss.
Replace the head or.................JB Weld it. Doesn't recommend it, won't guarantee it, but would at least try.
Gave it a try. My mom drove the car for another 20k miles, then sold it, it went to Texas and that's the last I heard of it.
I think about it from time to time, specifically with this thread.
How hot does a cast iron, Small Block Ford head get? Apparently not hot enough to affect JB Weld.

 

[WZ507]

Trying to think of another method...using a solvent to degrade epoxy. Some of the types used for dealing with petrol tank coatings should work...but effectiveness will come down to how much can reach the epoxy along the threading area.

Could also consider chopping off the stacks with a grinder and then using careful application of a dremel cutting wheel getting remaining threaded section out....

Consumer epoxies are generally quite high in x-link density which makes them difficult to swell with solvent, especially when they are in the glassy state (at room temp). When they are heated slightly (160F and above) and in the rubbery state they would be dramatically more susceptible to swelling, but then comes the challenge of getting them in the correct solvent (need a solvent with boiling point above 160F) and then you still have to deal with flammability (which most solvent have) at elevated temperature. This is probably an experiment that should be discouraged on the kitchen gas range top. Boiling in a water/glycol solution for an extended length of time may pay dividends here. If it were automotive glycol it would also have corrosion inhibitors present to minimize any corrosion that might occur. If trying this I’d look for a propylene glycol based coolant.

If the stacks are to be sacrificed, I think your idea of using a Dremel tool is an excellent one. It would be straight forward to fit a small burr to a die grinder and judiciously begin removing material around a small section of the velocity stack circumference and keep inspecting with magnification so see when the thread begins appearing. When you establish a small section (3/8” long and the full thread width) where the threads are clearly visible, with application of modest heat you should be able to use a pic, or pic and small hammer to break the stack threaded band at which point you should be home free. From there on out the remaining stack band should peel off like removing a broken band from a Mason jar. But again has to be peeled at elevated temp so epoxy is not glassy and high strength.

 

[Torontonian]

Another great thing about JB weld , inflatable boat , toy , ball , pool etc. motorcycle and bicycle puncture repairs. WAY better than sometimes supplied repair kits based on patches and rubber cement evaporative based glues . Roughen surfaces first obviously for adhesion. I'm still using my inflatable boat after 3 years with a puncture and check it before going out every time. Hard as a rock and welded to the surface. Patches can't even approach that. A motorcycle tube situation should be changed out for a new one after the puncture event at first reasonable opportunity. Disclaimer applies so don't sue me. Enjoy.

 

[MexicoMike]

I don't want to damage the stacks (or the carbs) so either they stay as is or are removed in one piece. The latter doesn't seem likely to happen so I figure I now own a set of Amal Concentric Premiers with permanently attached velocity stacks! So I'll look at the filter socks. I was also just now wondering if I could use the ham can filter and fabricate some sort of gasket that would seal the front plate of the ham can to the stacks. One problem with that solution is that with the stacks mounted, the mouth would be about an inch from the rear plate of the ham can. I have no idea if that proximity would interfere/alter airflow so as to obviate the benefit of the stack.

 

[WZ507]

I've been watching this with interest as my introduction to JB Weld was back in the 80's.
Had the heads off of a SBF for a valve job. Machine shop called and informed me we had cracked rocker boss.
Replace the head or.................JB Weld it. Doesn't recommend it, won't guarantee it, but would at least try.
Gave it a try. My mom drove the car for another 20k miles, then sold it, it went to Texas and that's the last I heard of it.
I think about it from time to time, specifically with this thread.
How hot does a cast iron, Small Block Ford head get? Apparently not hot enough to affect JB Weld.

A liquid cooled automotive head will run somewhere near the coolant temp - 200F? - unless we were talking about something extremely close to the EX port where it would be higher. That said the epoxy would have been in the rubbery state when the engine was hot, so pretty weak. I have no idea what the repair you refer to involved, but just thinking out loud I’m envisioning a hairline crack radiating out from the stud mount on the boss. I’ve personally seen several cast iron motorcycle cylinders with cracks radiating out (away from the bore) from threaded head bolt holes that never progress into anything serious. Perhaps the JB was applied in the stud hole and performed extraordinarily, where the boss would have failed rapidly without it. Or, IMHO more likely is the same repair scenario, but the crack never would have propagated with or without the JB. We’ll never know but to each his one truth in the matter.

If it were a stripped out head bolt, we know that it would be a joke to put in JB and expect that to hold. JB is no helicoil even though it can be drilled and tapped and is a structural material at RT. I am not down on JB as it is just another RT cure epoxy and I use lots of RT cure epoxies (including JB), and at elevated temp too. But I’m mostly using them for port filling were they have no structural function whatsoever.

 

[comnoz]

Personally I would use some tin snips and cut the stacks down to the carb and then grab them with some pliers and peel them off.
Then a fine wire brush in a bench grinder will remove all traces of JB weld.

 

[cyclegeezer]

I don't want to damage the stacks (or the carbs) so either they stay as is or are removed in one piece. The latter doesn't seem likely to happen so I figure I now own a set of Amal Concentric Premiers with permanently attached velocity stacks! So I'll look at the filter socks. I was also just now wondering if I could use the ham can filter and fabricate some sort of gasket that would seal the front plate of the ham can to the stacks. One problem with that solution is that with the stacks mounted, the mouth would be about an inch from the rear plate of the ham can. I have no idea if that proximity would interfere/alter airflow so as to obviate the benefit of the stack.

Too bad Burlen doesn't sell just the bodies.

 

[o0norton0o]

Personally I would use some tin snips and cut the stacks down to the carb and then grab them with some pliers and peel them off.
Then a fine wire brush in a bench grinder will remove all traces of JB weld.

I thought something similar. I would used the abrasive wheel instead of the snips to cut the stacks. Then cleanup the carb mouths carefully with an abrasive brush wheel, done!