Since I have a few ruined rocker cover stud threads on my bike, I've picked up a broken engine crankcase from a workshop nearby to practice with a cheap set of 10mm M6 helicoil thread repair inserts.
First experiment, I tried to damage an alloy thread of the case just by over-tightening a bolt. I grew up hearing "you think you're smarter than the next guy?", and indeed if POs can ruin threads by accident, so can I.
I was unsuccessful, the (standard quality stainless steel) bolt head went first. I thought length was probably a factor, so I tried with only 5mm of thread, and this time I managed to ruin the thread in the case. The coil in the second picture is the alloy of the case.
Most likely temperature plays a role, as well as the relative quality of both elements. So could a few grains of sand, maybe. Or starting off-thread / misaligned without noticing if you don't screw it in by hand first. Picking the wrong screw could also be a possibility, in bike shops mixing imperial and metric. Anyway, I had to work really hard, threads on this particular alloy crank case are not that easy to ruin.
So I drilled out the holes, to simulate worn threads.
Anyway, second experiment, I installed a thread insert. Seems to fit nicely. I cut one open, out of curiosity. The top 10mm is the insert, the rest is just the threads I've tapped to the bottom of the hole for nothing.
Obviously longer inserts would be better in this spot, but these 10mm ones came with the set and were perfect for fooling around. Notice the small bit at the bottom, which is the part you break off at the end and falls to the bottom.
Anyway, I renewed the only-5mm-deep overtightening-until-breakage. The bolt thread went flat, not the thread insert.
The insert suffers a little bit of damage though, and the third time around, it really started coming off.
It's easy to extract, and even though the first millimeters of tap were damaged, I was able to re-install a new insert.
Third experiment, since I've noticed that when you install a thread insert with Red Loctite, some of it can seep through the coil, I have installed an insert with too much Loctite and put a screw in right afterwards. When turning it back, it clearly shows the phenomenon.
I've let it dry all night, in this position, because I was curious what would happen when trying to remove the screw. The thread stays in place nicely.
Abusing this thread afterward again resulted in bolt breaking rather than thread, even though the very top of the insert has suffered a bit.
Not sure whether this is the best use of my workshop time, but I'm just at the beginning of a long learning journey, and also afraid to mess up this nice engine so I really take it easy. And thought I'd take a few pictures and share them. Not sure whether it is welcome, since it has nothing to do with the XS, now that I think of it. Please let me know.
I'm still waiting for a set of thicker inserts, and will run the same tests with those. Will keep you posted if interested.
First experiment, I tried to damage an alloy thread of the case just by over-tightening a bolt. I grew up hearing "you think you're smarter than the next guy?", and indeed if POs can ruin threads by accident, so can I.
I was unsuccessful, the (standard quality stainless steel) bolt head went first. I thought length was probably a factor, so I tried with only 5mm of thread, and this time I managed to ruin the thread in the case. The coil in the second picture is the alloy of the case.
Most likely temperature plays a role, as well as the relative quality of both elements. So could a few grains of sand, maybe. Or starting off-thread / misaligned without noticing if you don't screw it in by hand first. Picking the wrong screw could also be a possibility, in bike shops mixing imperial and metric. Anyway, I had to work really hard, threads on this particular alloy crank case are not that easy to ruin.
So I drilled out the holes, to simulate worn threads.
Anyway, second experiment, I installed a thread insert. Seems to fit nicely. I cut one open, out of curiosity. The top 10mm is the insert, the rest is just the threads I've tapped to the bottom of the hole for nothing.
Obviously longer inserts would be better in this spot, but these 10mm ones came with the set and were perfect for fooling around. Notice the small bit at the bottom, which is the part you break off at the end and falls to the bottom.
Anyway, I renewed the only-5mm-deep overtightening-until-breakage. The bolt thread went flat, not the thread insert.
The insert suffers a little bit of damage though, and the third time around, it really started coming off.
Third experiment, since I've noticed that when you install a thread insert with Red Loctite, some of it can seep through the coil, I have installed an insert with too much Loctite and put a screw in right afterwards. When turning it back, it clearly shows the phenomenon.
I've let it dry all night, in this position, because I was curious what would happen when trying to remove the screw. The thread stays in place nicely.
Abusing this thread afterward again resulted in bolt breaking rather than thread, even though the very top of the insert has suffered a bit.
Not sure whether this is the best use of my workshop time, but I'm just at the beginning of a long learning journey, and also afraid to mess up this nice engine so I really take it easy. And thought I'd take a few pictures and share them. Not sure whether it is welcome, since it has nothing to do with the XS, now that I think of it. Please let me know.
I'm still waiting for a set of thicker inserts, and will run the same tests with those. Will keep you posted if interested.
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The bottom stud on the RH front valve cover is the only "Common" stripped stud I find, I think it's cuz there wasn't enough room for a good deep hole there. Perhaps why the 4 bolt cover stayed on the LH side even though the compression release was quickly dropped.
