73 CB750 bolt stuck

[Bobby Joe]

So my dad is swapping his HM341 pipes to a set of 4-1 MACs and it has been nothing but hell for him...well, 2 of the bolts have been. One of the bolts is seized in the head and nearly behind the frame. It looks like we may have to slide the engine over to even attempt getting that one out. The other one is directly accessible, but it will not budge. He has snapped 3 extractors already and has supposedly tried heating it up at least one of the times beforehand. Does anybody have an idea of where to go from here? I was suggesting to him to drill it out and helicoil it, but what sort of drill bit will he need that can make it through considering all the extrators that have failed? And you would have to get that hole damn straight, which may be easier said than done at that angle.

Ideas? Thanks!

 

[Bobby Joe]

And somewhere along the lines...it earned a sexy lil crack...wonderful.

 

[dualitymike]

I had the same problem with one of the cylinder studs on my top case. Also broke off an extractor. If the piece of the extractor is stuck in the bolt now, the only thing that will get through it is tungsten. The extractors are hardened steel. I used this dremel bit and CAREFULLY ground out the piece of the extractor. I say carefully because it's easy to drift off course and get into the original threads and take out some of the surrounding aluminum, which is obviously a bad thing.

http://www.dremel.com/en-ca/Accessories/Pages/ProductDetail.aspx?pid=9901

Once you're past that, any drill bit should be able to get the rest of the bolt out. Then helicoil it.
Good luck,

 

[Hoosier Daddy]

With the two broken bolts and the cracked boss, I vote to pull the head and take it to a Machine shop. Have them remove the broken pieces, weld up, drill and retap the threads in the cracked boss,.
Then when you get it back clean up the ports and combustion chambers, lapp the valves and replace the valve seals.
Then couple gaskets and you have a fresh top end for his new exhaust.

 

[vbtravisd]

I usually take a nut with the hole close to the same size as the bolt and set it on top... then I weld the nut to the broke off bolt (fill the hole in the nut with weld). Let it cool, then put a wrench on it... it usually busts the weld, get new nut... repeat. Most likely 2-3 times and I can back out the broken bolt.

 

[Bobby Joe]

I had the same problem with one of the cylinder studs on my top case. Also broke off an extractor. If the piece of the extractor is stuck in the bolt now, the only thing that will get through it is tungsten. The extractors are hardened steel. I used this dremel bit and CAREFULLY ground out the piece of the extractor. I say carefully because it's easy to drift off course and get into the original threads and take out some of the surrounding aluminum, which is obviously a bad thing.

http://www.dremel.com/en-ca/Accessories/Pages/ProductDetail.aspx?pid=9901

Once you're past that, any drill bit should be able to get the rest of the bolt out. Then helicoil it.
Good luck,

I'm not sure if I mentioned that or not, but it is the extractor stuck in the 1st hole. I will attempt the dremel method first. Hopefully there is enough bite left with that cracked section.

I usually take a nut with the hole close to the same size as the bolt and set it on top... then I weld the nut to the broke off bolt (fill the hole in the nut with weld). Let it cool, then put a wrench on it... it usually busts the weld, get new nut... repeat. Most likely 2-3 times and I can back out the broken bolt.

I forgot about this method. I may try this for the second bolt. There is not a lot of room here since it is pretty close to the left down tube.

With the two broken bolts and the cracked boss, I vote to pull the head and take it to a Machine shop. Have them remove the broken pieces, weld up, drill and retap the threads in the cracked boss,.
Then when you get it back clean up the ports and combustion chambers, lapp the valves and replace the valve seals.
Then couple gaskets and you have a fresh top end for his new exhaust.

I mentioned this method to him. I guess this would be the last resort. I will need to find a good machine shop.

 

[TheJester]

With the mounting boss being cracked like that, there is no way a helicoil nor any other repair method will last. It has to be knocked down, built up, and re-drilled.