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Offline JWB

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(Success) Broken exhaust stud method question
« on: July 09, 2020, 06:53:07 AM »
After reading through the various threads involving removing broken exhaust studs it seems like there is a general consensus on this method.
1. Accurately center punch the broken stud.
2. Drill down the center of the broken stud with a 5/32 carbide bit.
3. Drill down the 5/32 hole with a left hand drill bit applying WD-40, PB blaster and or heat to assist.
Question: What size left hand drill bit?  5/32 is .156 and a #9 which is used to tap a 6mm hole is .196 so that doesn't leave much room for the left hand bit to grab on to.  This is also assuming you have drilled the initial 5/32 dead center in the broken stud.

The safest route is probably to take it to a motorcycle shop that has experience do this, but it is also the most expensive.
« Last Edit: July 14, 2020, 04:30:05 PM by JWB »
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Offline Nicklopic

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Re: Broken exhaust stud method question
« Reply #1 on: July 09, 2020, 07:57:45 AM »
The using a left hand bit to start is to hopefully get it to budge before even trying to use an easy out or drilling and tapping. Idk what other people do but it seems you're missing a couple steps.

Personally I think welding a nut to a broken stud is the all end all best method whenever it's a possibility.
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Offline JWB

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Re: Broken exhaust stud method question
« Reply #2 on: July 09, 2020, 08:34:30 AM »
In my case I have two studs that are broken off flush or just below the surface of the engine casing so welding a nut on the stub is not an option.  I think someone before me had attempted to remove them since they snapped off with only a minimal amount of pressure when I removed the exhaust system.  All other studs came out without an issue.  Years ago I remember doing this on a tractor exhaust manifold.  Of course that was a larger stud.  It that case I used a punch to flatten out the end of the broken stud so that I had an even surface to center punch. I figure to do the same in this case, but things are much tighter with a 6mm stud.
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Offline Don R

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Re: Broken exhaust stud method question
« Reply #3 on: July 09, 2020, 08:52:52 AM »
 Even when they are broken off flush or slightly in I've welded a washer to a broken bolt. Sometimes it takes a few tries. I turn it with a good set of channel locks.
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Offline Nicklopic

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Re: Broken exhaust stud method question
« Reply #4 on: July 09, 2020, 08:58:38 AM »
You can do a little bit of a build up on the end of the stud before attempting to weld the nut on. I just find it works better than easy outs without the risk of breaking an easy out and reallllllyyyyyy ruining your day
If you don't want to weld, I'd say left handed bit and and easy out that matches the suggested diameters. If that fails just drill and tap a new hole
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Offline JWB

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Re: Broken exhaust stud method question
« Reply #5 on: July 09, 2020, 09:05:46 AM »
I do have a 5/32 plus the #9 and a 6mm tap which was my first thought on how to remove these.  I don't have a welder in my meager home tool depot.  Plus it has been 40 years since I did any welding and figured an engine block is not something to practice on.  I know making sure the engine block is secure and not able to wobble then drilling easy and slow are key to not breaking off the drill bit inside the stud and as you said, ruining my day.
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Offline bryanj

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Re: Broken exhaust stud method question
« Reply #6 on: July 09, 2020, 12:06:30 PM »
Been doing this a long time ans easyouts never work in that situation.
Make sure tou start in centre at the correct angle with tiny drill ang go out in steps till 5 mm which is i think tapping size for 6mm thread. If you got it right the thread remains should come out. If you can get a left hand 4.5mm drill and are incredibly lucky that might unscrew what is left whilst trying to drill
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Offline dazemc

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Re: Broken exhaust stud method question
« Reply #7 on: July 09, 2020, 04:55:24 PM »
I'm convinced that easy outs are only for bolts/studs that have broken off and not seized. I've never had any luck with a seized and broken bolt/stud coming out with one.
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Offline BenelliSEI

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Re: Broken exhaust stud method question
« Reply #8 on: July 09, 2020, 05:32:35 PM »
+1 t Bryanj. Last time I did what he suggested, the heat and counter rotation of the bit took the remnants right out! Good Luck!
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Offline Sano

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Re: Broken exhaust stud method question
« Reply #9 on: July 10, 2020, 07:15:37 AM »
I think Bryanj is right, the only way I got Two very stuck broken studs out was welding nuts onto top of broken studs with a powerful high amp electric welder.  The rest of the block was shielded with some sheet metal.  After good high penetration welds apply heat to case at base of stud( mapp gas torch works if you don’t have acetalyne) and then use a cordless impact wrench to back them out.  Every other attempt proved frustrating and useless.  When they finally backed out it was a very good feeling.  Good luck!
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Offline madmtnmotors

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Re: Broken exhaust stud method question
« Reply #10 on: July 10, 2020, 07:31:24 AM »
What motorcycle uses a 6mm exhaust stud? CB750 uses 8mm studs...
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Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
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Offline bryanj

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Re: Broken exhaust stud method question
« Reply #11 on: July 10, 2020, 07:55:34 AM »
350,400,500,550,650 and all the twins plus i think the 750 with stubs
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Offline madmtnmotors

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Re: Broken exhaust stud method question
« Reply #12 on: July 10, 2020, 09:28:16 AM »
Quote from: bryanj on July 10, 2020, 07:55:34 AM
350,400,500,550,650 and all the twins plus i think the 750 with stubs

The 750 uses 8mm studs. Which one uses 6mm studs?
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Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

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Offline bryanj

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Re: Broken exhaust stud method question
« Reply #13 on: July 10, 2020, 11:08:30 AM »
You may well be right, i was talking about the SCREWS on the original stubs not the studs on the later ones. Its been 40 years since i took any out so that is why i said I THINK
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Offline Don R

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Re: Broken exhaust stud method question
« Reply #14 on: July 10, 2020, 12:02:03 PM »
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Offline Stev-o

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Re: Broken exhaust stud method question
« Reply #15 on: July 10, 2020, 02:12:23 PM »
Quote from: JWB on July 09, 2020, 06:53:07 AM

The safest route is probably to take it to a motorcycle shop that has experience do this, but it is also the most expensive.

I would not take it to a bike shop!  Maybe a machine shop....
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Offline dave500

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Re: Broken exhaust stud method question
« Reply #16 on: July 11, 2020, 02:27:56 AM »
most bike shops change oil and brake pads,something like this on an old bike is for someone who is actually enthusiastic about it.
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Offline Medyo Bastos

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Re: Broken exhaust stud method question
« Reply #17 on: July 11, 2020, 04:49:29 AM »
Quote from: Stev-o on July 10, 2020, 02:12:23 PM
Quote from: JWB on July 09, 2020, 06:53:07 AM

The safest route is probably to take it to a motorcycle shop that has experience do this, but it is also the most expensive.

I would not take it to a bike shop!  Maybe a machine shop....



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Offline JWB

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Re: (Success) Broken exhaust stud method question
« Reply #18 on: July 14, 2020, 04:41:46 PM »
Using my basic approach plus the tips and hints you added I successfully drilled out the broken studs and re-tapped the holes. 
Got a nice center punch in the middle of the stud, used 3 different drill sizes ending with the #9 then tapped the holes.  I went nice and slow and used a slow speed with a handheld variable speed hand drill cleaning often with plenty of WD-40 to keep things cool and clean.  I was worried about drilling down the center of the stud without drifting into the aluminum casting.  Left and right wasn't too bad as the angle of the stud matches the surface where the stud hole is, so I just did that visually.  To keep the drilled hole level up and down I first screwed in a couple of studs and put a small level on them then leveled the engine until i had mid-bubble.  My drill has a level on it so as long as I kept it level I knew I was at least close to staying in the middle of the broken stud as I was drilling it out.
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Offline ekpent

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Re: (Success) Broken exhaust stud method question
« Reply #19 on: July 14, 2020, 05:05:02 PM »
 Congrats on gittin' her done ! So far the only time I have had to drill one out was on a Suzie GT750 and they are notorious for breaking. I'm sure you will agree that its kind of a stressful job.
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Offline JWB

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Re: (Success) Broken exhaust stud method question
« Reply #20 on: July 14, 2020, 05:31:09 PM »
Stressful for sure.  The worst part is when the drill breaks through the end of the stud and the drill bit catches.  Lots of holding my breath that the bit doesn't snap off.
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Offline Nicklopic

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Re: (Success) Broken exhaust stud method question
« Reply #21 on: July 14, 2020, 05:36:45 PM »
Pop some bubbly and celebrate the success! 🍾🥂
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Offline Medyo Bastos

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Re: (Success) Broken exhaust stud method question
« Reply #22 on: July 14, 2020, 06:03:26 PM »
Yeah pop some coochie for sure!


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Offline Alan F.

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Re: (Success) Broken exhaust stud method question
« Reply #23 on: July 14, 2020, 07:13:58 PM »
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Offline Nicklopic

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Re: (Success) Broken exhaust stud method question
« Reply #24 on: July 14, 2020, 07:57:23 PM »
Quote from: Alan F. on July 14, 2020, 07:13:58 PM
There's always these: https://racetechtitanium.com/product/titanium-m8x38-5-stud-38-5mm/
Side not, I've been seeing lately a ridiculous amount of titanium stuff being produced in the Motorsports world's. Like anything from nuts and bolts to brake pad heat shields for Subaru brembos. Did titanium all of a sudden become affordable?
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