Stripped exhaust bolt, very messy attempt

[tbrand69]

Alright so I totally f4cked up the extraction. There used to be a al little nub sticking out, like this:

Tried welding a nut onto the end, and that worked for half a turn until the rest of the protruding bolt snapped off. So then all I had left was a bolt that was flushed to the engine.

So I figured I'd try the left handed drill bit method. I drilled a pilot hole, then sent in a larger lefty to finish up. Unfortunately, the lefty snapped off about a quarter inch into the hole. And then I got angry and started drilling and beating a punch into the hole. It's messy now:

God that looks awful. So I'd rather avoid taking the head off and paying a machine shop to drill out the hole and retap it, so do you guys have any suggestions? I feel real bad and embarrassed about this, as it reflects on my ability to get things done. But all I care about is getting this thing fixed.

Tommy

 

[1980GS1000E]

I know that feeling. I tried an ez out that then broke off. I would try drilling a small hole to the side of the broken bit. Then another on the opposite side. You may be able to loosen the broken piece and get it out. Then use progressively larger bits to remove what's left. Drill all the way thru the frozen bolt. There is some space behind it. After it's out, helicoil your way to freedom.

 

[hampshirehog]

I would weld another nut on there. Just stick a blob of weld on first to give the nut something to sit on.

 

[GateKeeper]

I had to drill mine out completely, then get it filled with weld, then drill and tap a whole new hole

and after bieng painted you can't even tell

.

 

[posplayr]

I had to drill mine out completely, then get it filled with weld, then drill and tap a whole new hole

Thanks for showing that, never heard or seen it done.

 

[GateKeeper]

no problem,,,,,,I had no choice but to drill the hole even bigger, you need to get all of the metal out from the bolt, and then had it filled with aluminum weld, we found center, marked it, drilled it and made a new thread....no jigs used, it was all eye balled, I did put the exhaust header on, to at least get an idea of where we needed to drill, and we put in a few long bolts in the other hole to get an idea for the angle...

lucky me it worked.....

.

 

[Badooka]

Awesome fix! Looks great as well!!!!! Does that paint give you any overheat issues??

 

[Thumper88]

Try welding on the bolt and building it up so it sticks out. You can try welding a nut onto that, but I've had better luck using vise grips on said weld.

 

[GateKeeper]

Awesome fix! Looks great as well!!!!! Does that paint give you any overheat issues??

Thanks....

I don't think, there will be an issue with heat, I at least hope not, but I will find out soon, bike has not been running yet, I am almost done the rebuild, so I will know soon....

It's just regular engine paint....

 

[tbrand69]

Okay so I admitted defeat. I'm just going to drill out the entire area--bolt, threads and all. I read a tech article about drilling the hole larger than stock, then tapping it for a larger bolt. I would seal the larger bolt shaft in there, then drill and tap that to the stock 8mm size. I can't weld aluminum so this would be simpler choice. Bad thing is that I have to remove the heads from the engine; I have almost no leverage to drill anything with everything still in the frame.

I'll worry about this later. Once I get the carbs rebuilt, the sprockets and chain replaced, and the forks reconditioned, I'll pull the heads and do what needs to be done, then reinstall and check the valves. Then I can finally tune the damn thing.

Tommy

 

[GateKeeper]

Since you are not able to weld, then your going the Heli-Coil route

Helical insert

Helical inserts, more commonly known by the trademark Heli-coil,[7] are inserts made of coiled wire. The insert is inserted into a tapped hole that is larger than the desired hole. They are usually over-sized so that they anchor themselves. Some have tangs to install them while others don't. Special tools are required to install the inserts.[3][8

Don't do what you wrote lots of work, and you will be in a bigger mess....

lots of info on heli-coil inserts

https://www.google.ca/search?q=heli...s=org.mozilla:en-US:official&client=firefox-a

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[1980GS1000E]

Keep in mind that there is not an unlimited amount of area around that bolt to play with. I had the same thing happen to me and succeeded a repair by drilling small, around 2mm, holes around the bolt along the thread line. Then I drilled and tapped for a helicoil. Swapping bolts for studs is a standard fix for this.

 

[gearhead13]

You will need to get the piece of drill bit out before you can drill it larger. I had the problem with a Yamaha I had, drilled it out (to 3/8" if i recall correctly) and tapped it for a chevy exhaust manifold stud.
I bought a set of studs for mine, so I dont have to worry about that happening again.

 

[tbrand69]

Since you are not able to weld, then your going the Heli-Coil route



Don't do what you wrote lots of work, and you will be in a bigger mess....

lots of info on heli-coil inserts

https://www.google.ca/search?q=heli...s=org.mozilla:en-US:official&client=firefox-a

.

Never heard of heli-coils, but I will definitely look into it. Thanks for the info.

Keep in mind that there is not an unlimited amount of area around that bolt to play with. I had the same thing happen to me and succeeded a repair by drilling small, around 2mm, holes around the bolt along the thread line. Then I drilled and tapped for a helicoil. Swapping bolts for studs is a standard fix for this.

Ah yes, the studs. Definitely something I'm interested in. I already started drilling the whole thing out with a 5/16 bit (I think, I'll double check); that's enough to bore out the bolt and the threads, and make it just slightly larger than stock. Probably not the right way but it's too late now. Wooo!

You will need to get the piece of drill bit out before you can drill it larger. I had the problem with a Yamaha I had, drilled it out (to 3/8" if i recall correctly) and tapped it for a chevy exhaust manifold stud.
I bought a set of studs for mine, so I dont have to worry about that happening again.

From what I've drilled so far the bit that was stuck has already been chewed up, so at least that part is out of the way. I'd like to keep everything as close to stock as possible, so the studs I would buy would have to be the same diameter and thread, which is 8mm x 1.25 I believe.

Thanks for the reply guys, I'm getting some good info.

Tommy

 

[Steve]

Never heard of heli-coils, but I will definitely look into it. Thanks for the info.

I already started drilling the whole thing out with a 5/16 bit (I think, I'll double check); that's enough to bore out the bolt and the threads, and make it just slightly larger than stock. Probably not the right way but it's too late now. Wooo!

I'd like to keep everything as close to stock as possible, so the studs I would buy would have to be the same diameter and thread, which is 8mm x 1.25 I believe.

If you have already drilled it out "too big", it's the PERFECT time to install Heli-Coils.

Get the kit for the M8 x 1.25 threads, it has a special bit (or tells you what bit to use) and will also have the special tap to use. Install your coils and you are good to go.

Note: do not use that tap for ANYTHING else, the ONLY thing it is good for is installing M8 x 1.25 Heli-Coils.

.

 

[tbrand69]

If you have already drilled it out "too big", it's the PERFECT time to install Heli-Coils.

Get the kit for the M8 x 1.25 threads, it has a special bit (or tells you what bit to use) and will also have the special tap to use. Install your coils and you are good to go.

Note: do not use that tap for ANYTHING else, the ONLY thing it is good for is installing M8 x 1.25 Heli-Coils.

.

Perfect. I measured the depth of the other screw holes to about 25mm. I assume I should drill this guy out to the same depth?

Tommy

 

[Steve]

I would not go any deeper than the existing holes. You do not want to drill them all to match that one, they might not have the room behind them before getting into something that should not have an extra hole in it.

If you are going to install Heli-Coils in other holes, measure the depth of the hole, drill it larger, but not deeper, tap it, install the coil, move on to the next hole.

.

 

[tbrand69]

I would not go any deeper than the existing holes. You do not want to drill them all to match that one, they might not have the room behind them before getting into something that should not have an extra hole in it.

If you are going to install Heli-Coils in other holes, measure the depth of the hole, drill it larger, but not deeper, tap it, install the coil, move on to the next hole.

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Oh no no no, just the one hole lol. I see no reason to install the coils in the other holes. They are perfectly fine and good to go. I will probably install studs on them at some point, though.

 

[tbrand69]

I would not go any deeper than the existing holes. You do not want to drill them all to match that one, they might not have the room behind them before getting into something that should not have an extra hole in it.

If you are going to install Heli-Coils in other holes, measure the depth of the hole, drill it larger, but not deeper, tap it, install the coil, move on to the next hole.

.

Actually I had a question. Upon further research, it says the M8 coil requires a 1/4 inch bit and hole. I have started drilling the hole with a 5/16 bit, so it's 1/16 larger. Common sense tells me that this will be a problem when trying to install the coil.

The hole should be about 25mm deep, and I have only drilled down to about 5mm. I could conceivably drill the remaining 20mm with the correct 1/4 inch bit. My question is: would it be okay to have the new coil threads starting 5mm below the surface of the hole? As a result, there would be a 5mm gap where there are no threads. Would that severely compromise the strength of the mount?

Tommy

 

[Steve]

Actually I had a question. Upon further research, it says the M8 coil requires a 1/4 inch bit and hole. I have started drilling the hole with a 5/16 bit, so it's 1/16 larger. Common sense tells me that this will be a problem when trying to install the coil.

I am not near my helicoil set to verify, the 1/4" bit seems a bit small, bit might actually be correct.

The hole should be about 25mm deep, and I have only drilled down to about 5mm.

What makes you think the hole needs to be that deep? How deep is the original hole?
I would not go any deeper than that, there are oil passages and whatnot lurking just below the surface.

My question is: would it be okay to have the new coil threads starting 5mm below the surface of the hole? As a result, there would be a 5mm gap where there are no threads. Would that severely compromise the strength of the mount?

See my previous comment, I think the only thing that will compromise your strength will be drilling into a void.

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