First of all, this work was performed in my Sanglas bike. It doesn't apply to our Hondas, but I thought you may find it interesting, as it is a new skill for our "bag of tricks".
The exhausts are original and unobtainable. They are in a pretty decent shape, but the heat shields are stuck into place. Some bolts can be removed, some others are stuck and the head disintegrated, some others simply snapped off, and some others turn but don't unscrew.
They are so rusted that the head simply disappears under the screwdriver force.
Seems that is time to call the army. First thing, to remove the bolt. It is necessary to drill the head, carefully not to damage the heat shield.
Once done, the remains of the bolt protrudes. We have to cut if flush, either with a hacksaw or a Dremel tool..
Carefully, we must make a centered drill over the remains of the bolt, and gradually increase the diameter until we can tap a new M5 thread. The nut turns with the tap so we need vise-grips to hold the nut in place.
If the hole is centered the result is satisfactory....
...but it is not as easy as it seems, therefore in some other holes the result is lousy. Not even a helicoil can be used to fix that damage.
I was convinced that the threads were machined at the factory, even before the exhaust was assembled. Asking here and there I knew about something called "rivet nuts". And after seeing some pictures, it seemed that it was exactly what I had been fighting against. I had to decide between leaving a crappy exhaust, using a home-made solution to rivet the nuts or biting the bullet and spending 100 euro to buy a tool I may never use again. But again, asking here and there I was able to borrow the tool and nuts for a whole afternoon. Get down to business!!!
The tool is very similar to a common riveter. It has different tips according to the size of the nut. The nut is threaded in full, because the rivet tool will "pull" from the threads, and so the "hat" portion will mushroom and rivet to the sheet metal.
First thing first, remove the old nuts. New ones had 7mm diameter. With a 8 mm drill bit, I slowly drilled the old nut -using the vise grip when necessary-. It is better to fall on the safe side and finish to break the nut with a chisel, than drilling past the nut and enlarging the hole. At the end, the easiest way is to use a 7mm drill bit all the way through.
With patience, all the old nuts are removed and the new ones in place...
And, after shaking the exhausts, we get the remains of the old nuts...
Now it is a matter of painting the heat shields, polish the chrome and use new, stainless bolts, and the exhaust will look just like new!!!
