1984 GPZ550 - Exhaust Stud Broke off in Head

www.partzilla.com/product/kawasaki/92004...982697d4b089404db361

Somebody really F'ed up the threads in the hole, not to mention the metal around the hole.  My condolences.  

Yup... free motorcycles always come with some previous owner fuckery...

Tfest, you say the end of the broken stud is "deep"; how deep? This will affect possible removal methods.

If it's deep enough such that the threaded hole above it will give enough location for a drilling bush, I'd go that route. I managed to get broken M7 titanium bolts out of a car wheel rim this way. I used normal right hand drills, drilled in steps to the minor diameter of the stud. Once this was done, I could get pliers on th end of the remaining helix and pull it out in a spiral.

The minor diameter of an M8 stud (most likely 1.25mm pitch) is between 6.272mm and 6.619; I'd go up to 6.5mm in 1/2mm steps from 5mm. Something like that.

I made my drill bushes out of the thread of an old bolt, so that it screws into the hole above the stud. I have a lathe, so making the hole was easy. Without a lathe, try holding a piece of M8 thread in the chuck of a battery drill, hold a 5mm drill bit in a vice and "reverse drill" the hole; it'll get you close.

Ian

Page 1 should have a picture of the stud. It's about a half inch deep, the PO drilled it out incorrectly...

wrote:

Somebody really F'ed up the threads in the hole, not to mention the metal around the hole.  My condolences.  
 

It looks like someone snapped the stud, and then used an angle grinder in an attempt to cut a slot so they could take it out with a flat screwdriver. If you're taking out a stripped JIS or phillips head bolt that can work, but not with a stud that's bound in so tight that it snapped!

I agree with Ian_B - a drilling bush (ideally with a left-hand drill bit) would be the best option here to keep it even when taking the old stud out. Since the hole is so ruined to such a depth you might need to follow it with a larger size, then tap it, and use either a repair stud (if you can get one that fits) or a helicoil.

Once I removed a broken bolt from aluminium using acid but I don't remember what acid I used. I know it can be done with nitric and it won't harm the aluminium but will dissolve the steel.
Have a look see on google & youtube. It doesn't take long to loosen if the acid can penetrate the threads.

You can buy a proper sized bolt and drill a pilot hole with a lathe to give you a guide to drill the exact center of the broken bolt. But you’ll need some semblance of untouched aluminum in the bolt hole to center it and you just may have some.
(But secretly I too am thinking.. my condolences.)



You can do it!