Engine mount broken bolt - KZ900 Lower Right

As you will note in the photographs, I have a broken right lower engine mount bolt on my 1976 KZ900 survivor restoration.

Until this problem, I have worked through most everything one would expect to find on a bike that sat under a deck for 15 years. This is going to be a nice bike and it is being restored with mostly OEM parts whenever possible.

The bolt was snapped at the surface. Some previous owner started drilling the snapped bolt, which is hardened....seriously hardened, and I tried to continue drilling hoping I could extract the broken bolt. Japanese steel from the 70s is some of the best steel made, and even a cobalt bit barely scratches the toughness f the bolt. The drilled hole was never centered and you can see where I'm at in the pictures.

Before going further, I wanted to consult with you all to pick your brains. Any ideas or suggestions are seriously welcomed.

I am thinking that maybe I should grind the threaded part in the frame down to surface and weld a bolt to the frame so that I have a 3rd attaching point.

So, thats where I'm at and any help is appreciated

I wouldn't grind anything.

Before going any further I would check around at several local machine shops to see how they would remove the broken bolt. They may suggest using Metal Disintegration Machine (MDM) or Electric Discharge Machine (MDM) to simply disintegrate the broken bolt, or they may offer an easier solution. Keep in mind that folks who work in machine shops encounter these types of problems fairly frequently and have experience in solving similar problems without creating bigger problems. Ed

Thanks, Ed, I am following your advice and waiting to hear from a local shop.

Whenever someone called me to take one out I asked them if they had tried. If they had I wouldn't touch it!:dry: :laugh:

Just to conclude this thread I wanted to show the result s of my effort to extract the hardened broken bolt from my KZ 900 / 1976.

I extracted the broken bolt with an adjustable speed Dremel tool using Dremel tungsten carbide cutters ($10 each).

I used low speed and drain oil for cutting oil. It took about 4 hours total. My process was to used a center punch to create dimples in the broken bolt and then ground the dimpled surface with the tiny Dremel bits whatcha are harder than hardened steel.

I need to retap the threads, and clean out the existing threads which are mostly intact. Drills did not work, even cobalt drills did little more than polish the broken bolt. I prefer not to have to do the job again .....ever, if possible

Before and after pictures attached.