My Sweet Thing K1100RS has been trouble free since I bought her in early 2016 but recently after a 10,000km tour of Vic, Tassie and southern NSW I've found that the very front exhaust stud has fallen out.
Inspection reveals that the previous owner had stripped the stud hole in the head and installed a Helicoil. In doing so the head around the stud hole has cracked and he's glued it back together with epoxy. It's a mess. The helicoil is partly exposed and of course the stud just won't tighten up at all.
I've had an automotive engineer inspect it and he says he can build it back up with alloy weld but I need to take the head off for him to do that properly. That's ok, no problem there, but he's also suggested that I'd be better just to repair it with JB Weld. It's certainly a much quicker and cheaper solution.
I've had a look at the specs on JB Weld. Two products might be suitable.
JB Weld Original Cold Weld Epoxy - 3,000psi up to 250ºc Data sheet here
JB Weld ExtremeHeat - 500psi up to 1,300ºc

So the idea will be to get the old helicoil out.
Roughen all the surfaces. Clean it up and degrease.
Fill the stud hole and surrounding area with JB Weld epoxy.
Re-drill and tap.

Wondering if anyone has had any experience doing this? Is it going to work? There's a large amount of tensile force on a stud and the heat will be quite high.
I'd like to use the JB Original Cold Weld because it appears to have the greater strength but only rated to 250ºc. The exhaust would probably get a lot hotter than that but maybe not the alloy.
Any thoughts and suggestions before I attack this would be very welcome.
Cheers

Hi welding will cause some distortion we don't know how much but is the best solution Ask your man,Email
JB with your query they know the  best.product to use

I would weld it. Where it is it would be a difficult job and probably not permanent the rapid and repeated heating and cooling would be a real problem for any epoxy.

RicK G wrote:I would weld it. Where it is it would be a difficult job and probably not permanent the rapid and repeated heating and cooling would be a real problem for any epoxy.

+1  I suspect that using JB weld will only delay the final reckoning with the welder.  Better to bite the bullet now. 

Having pulled the cylinder head on a brick engine and breaking a head bolt in the process, I would pull the whole engine or possibly see if the welder can do the job while the engine is in the bike and the bike is on it's side.

Anything to avoid dealing with the head bolts.  The upper rear bolt especially seems to be in a spot that allows water to get down into the threads causing corrosion between the bolt and the block.  Took me two weeks to get the broken part of that hardened bolt out of the block and install a Helicoil in the hole.   I learned a lot of new words doing that job.

RicK G wrote:I would weld it. Where it is it would be a difficult job and probably not permanent the rapid and repeated heating and cooling would be a real problem for any epoxy.

I would agree Rick. I'd be far happier with it welded properly but having this option presented to me I feel I need to explore. I've shot JB Weld in the US an email already and we'll see what they have to say.

Point-Seven-five wrote:.... I would pull the whole engine or possibly see if the welder can do the job while the engine is in the bike and the bike is on it's side.

I did discuss that with him but he said to do it properly he needs to be able work on top of it.
Also he wasn't all that confident about actually filling the hole. Difficult he says to get the alloy weld to run in there without causing other problems. So this also presents another problem in that it may be difficult to accurately drill and tap if the hole is a 'dog's breakfast'.
Maybe I need to grind the area right down to expose more of the hole so it can be built up evenly. Just some thoughts.

Thank for the input.
At this point I'm going to wait and see what JB Weld has to say and I might also see if I can get a second opinion from another engineer.
In the meantime I'm trying not to ride the bike too much atm but I am enjoying the grunty note I'm hearing.

Whatever route you take, I think you'd be very lucky to end up with a perfect repair: At the lower end of the success scale an epoxy repair at best will only last for so long, and at the upper end of the scale a good enough weld (cast ally is tricky & not all ally welders are equal btw) will still be likely to result in an off-centre and weak threaded hole.

Nothing wrong with any of those results, because the cost/effort of your chosen repair route will be directly reflected on the eventual success scale; which I think answers your initial query. But you'll only ever score a ten with a replacement head - only my opinion.

With new gaskets and nuts how much torque is really needed on the studs anyway? Mine are not heavily torqued.

Is it possible to drill and tap the hole a bit deeper. Even 10 mm would secure it better and aid the JB weld.
Regards Martin.

I often go for the quick El cheapo option cause I'm El cheapo. The JB lasted at least four years and x km, but actually x years and x km, you might find out from the previous owner.

You can get solid steel inserts, stronger and cheaper than Helicoils, I feel they don't go loose as easily as Helicoils.

You can get jewellery cheaper than Helicoils.....


And yep, I'd be starting with the bodge economically prudent options too: there's absolutely no harm because as Olaf says it's only an exhaust stud, so it's no crisis if successive 'experiments' fall apart straight away fail to meet requirements  . On a serious note, don't think that welding will automatically and easily give a perfect repair.

MartinW wrote:Is it possible to drill and tap the hole a bit deeper. Even 10 mm would secure it better and aid the JB weld.
Regards Martin.

 I know someone who did this and he struck water !

Would there be any advantage in using a Timesert rather than a Helicoil?

Ringfad wrote:

MartinW wrote:Is it possible to drill and tap the hole a bit deeper. Even 10 mm would secure it better and aid the JB weld.
Regards Martin.

 I know someone who did this and he struck water !

Typical bad luck. anyone else could have struck oil.

92KK 84WW Olaf wrote:With new gaskets and nuts how much torque is really needed on the studs anyway? Mine are not heavily torqued.

I agree. Not a lot of tensile force on the stud once it's torqued up.

chris846 wrote:... On a serious note, don't think that welding will automatically and easily give a perfect repair.

My thoughts exactly. Both guys I spoke to said it would be a difficult job to weld.

So I finally got this repaired.
I found another mechanical engineer to take a look and he suggested it would be better to grind as much of the alloy away from around the hole as possible and then build it back up. He was unsure if the repair could be done with the bike laying on it's side, so looked like the head would need to come off.
The advice I got from JB Weld in the US didn't inspire me with confidence. It just seemed to be a service desk jockey saying "yep, JB Weld can fix it."
I took it home and pulled the exhaust off and got the old Helicoil out and took a really good look. The PO's mechanic had made a real dogs breakfast of this. Here's a photo and you can see the remnants of epoxy he used to glue it back together.



The reason the helicoil had failed is because he'd only drilled and tapped the first 12mm into the hole. The remaining threaded hole into the head proper was the original M8. WHAT A DOOFUS!!!  I estimated there was at least 15mm or more, albeit damaged thread at the bottom of the hole and I reckon that's enough to hold the stud.
I drilled it out and tapped it to M10 right to the bottom. I figured a 10mm stud would hold better than using a helicoil. I'd called the last engineer guy to tell him that I was taking this route and asked him if he could turn down the end a M10 bolt to M8. No problem. He had an old Toyota head bolt that would do the job. It was ready the next day.


Went in like a dream. Exhaust back on and torqued up with new gaskets and nuts. Job done. After all the worry over this, it didn't take long at all and he charged me $30 for the stud.




To be honest, while I really wanted to repair this properly, I was also seriously considering the JB Weld option. As was pointed out above, what's to lose. Alloy welding is always an option if it fails anyway.
It's crazy but the very thing that caused the problem in the first place was the saving grace in the end.
Thanks for all the comments and suggestions. Cheers

That’s a really great repair - a really first rate engineering solution. Better than the original

Nice job, seriously.

From Holy Crap to channel No 5.Magic

Good fix

An easy fix in the end for sure but I think I was very fortunate.
I'm wondering though, just a hypothetical. If the M10 helicoil had been installed to the bottom of the stud hole and had failed, would there be enough metal around the hole to go to an M12.
I've never had the head off one of these and wouldn't have a clue where the oil and water lines are.

You'll probs find out by the time you're up to the M20 mark...

Just in case it needs re-doing at a later date, I have a better solution than JB Weld.


The Rootes Group had a problem of porosity with the engine castings for the Hillman Imp in the 60's and developed a product to fix the problem.
It was a liquid aluminium mixture that they put the castings into and it seeped into the cavities and sealed them off.
They later made various versions of it available and even developed and even Titanium versions.
It is still available today and goes by the name of Devcon.
I am not sure if you can get it in the original liquid format but I know they do many versions of it.
Those versions are applied like body filler.
These versions I have used a great deal in the past.
After application, to fill any holes, it can be worked and sanded just like body filler.
It can even be used to build-up damaged areas, drilled and tapped, as the parent metal can.
This is possible because it is around 80% aluminium.

I have found that after preparing the area as you normally would, it helps to flush it clean with something like acetone, to remove any grease or oil residue and give the Devcon the best chance of bonding cleanly to the parent metal. 

https://itwperformancepolymers.com/products/devcon

Hello Rob! You've broken cover then?

Dai wrote:Hello Rob! You've broken cover then?

Hello Dai,

I know.

It's been a while since I last posted on here.

I had posted a few times on BritChopper the other week.

That was the first time in ages as well.

Not been feeling "social" as such for a while and struggling but feel as though I am getting there, if still a little vague, if that's the right word.

Hope you are doing all right.

Still using the "Two step forward and one step back" system myself at present, though I think I have it in reverse. 

I am still trying to source an axle for my K100 trike project.

The original one fell though some time back and I just can't find one suitable.

Been thinking of perhaps a BMW 3 Series one but am not sure how it would effect the overall gearing.

All the Best,

Rob54.

Rob54 wrote:

Dai wrote:Hello Rob! You've broken cover then?

Not been feeling "social" as such for a while

Hi Rob,
Don’t see too many Kentish on here. If you ever get to feeling “social” again, I’m near Sandwich.
Cheers, Stu

tinyspuds wrote:

Rob54 wrote:

Dai wrote:Hello Rob! You've broken cover then?

Not been feeling "social" as such for a while

Hi Rob,
Don’t see too many Kentish on here. If you ever get to feeling “social” again, I’m near Sandwich.
Cheers, Stu

Hello Stu,

Not Kentish by birth but have lived down this way for over 25 years now, so perhaps an accepted "incomer" by now.

Thank's for the invite.

As soon as I get out of this funk (Man, Ha,ha) I may take a trip (Man, Ha, ha) out and see you.

Sorry, I must be going through another 60's/70's phase. 

I think it's the equivalent of us old un's going through a second childhood, or summat like that.

Now where did I put my Lionel's?

I like the outfit by the way.

All the Best,

Rob54

Rob54 wrote:

tinyspuds wrote:

Rob54 wrote:

Not been feeling "social" as such for a while

Hi Rob,
Don’t see too many Kentish on here. If you ever get to feeling “social” again, I’m near Sandwich.
Cheers, Stu

Hello Stu,

Not Kentish by birth but have lived down this way for over 25 years now, so perhaps an accepted "incomer" by now.

Thank's for the invite.

As soon as I get out of this funk (Man, Ha,ha) I may take a trip (Man, Ha, ha) out and see you.

Sorry, I must be going through another 60's/70's phase. 

I think it's the equivalent of us old un's going through a second childhood, or summat like that.

Now where did I put my Lionel's?

I like the outfit by the way.

All the Best,

Rob54

I’m a Bermondsey boy by birth. Cosmic. Been playlisting CSNY on a loop myself lately 

tinyspuds wrote:

Rob54 wrote:

tinyspuds wrote:
Hi Rob,
Don’t see too many Kentish on here. If you ever get to feeling “social” again, I’m near Sandwich.
Cheers, Stu

Hello Stu,

Not Kentish by birth but have lived down this way for over 25 years now, so perhaps an accepted "incomer" by now.

Thank's for the invite.

As soon as I get out of this funk (Man, Ha,ha) I may take a trip (Man, Ha, ha) out and see you.

Sorry, I must be going through another 60's/70's phase. 

I think it's the equivalent of us old un's going through a second childhood, or summat like that.

Now where did I put my Lionel's?

I like the outfit by the way.

All the Best,

Rob54

I’m a Bermondsey boy by birth. Cosmic. Been playlisting CSNY on a loop myself lately 

Hello Stu,

My wife's a Bermondsey lass.

I come from the other side of the water myself.

East-End, born and bred, until I became a reluctant exile. 

I used to listen a lot to CSN&Y but was more partial to a bit of "Pearl" and the BBHC myself, or some riffs from Jimi.

Seems the world has forgotten how to make good music nowadays for the most part and the stuff they do produce they mis-named by leaving the "C" off the beginning off the name of the genre, if you can call it a genre that is. 

It is probably why you see the ridiculous numbers of people listening to the old music on YouTube and such.

I think the world is crying out for decent music and all they are getting is the play-lists full or rubbish pushed down their throats.

I never believed I would ever get to a stage where I hated ANY form of music but some of it makes you feel as though they have found a unique way to create a dystopian future that even George Orwell could not have predicted.

Still, keep listening to the good stuff.

All the Best,

Rob54.

Wow that was a good fix and saved a fortune in parts and time. Well done sir!

Excellent result, ride safe.