This is where I'm going to be labelled a nerd, no doubt, but I'll stick to my guns because I think there is a small but important difference. The service manual specifies that the clearance between the shift pawl and the shift drum pins should be set by using the shank of a #32 drill bit. Simple enough, right? It's a convenient, and real-world way of finding something cheap and easily accessible through any hardware store, that has the correct dimension to set an important clearance in the shifting mechanism, without resorting to a specially made tool.
Except that a #32 bit is unheard of in Italy, and I would guess in Europe, where we use the metric system, including for drill bits. So, aside from the fact that I had a friend bring me a couple of drill bits from the US a few years ago, the fact is that nobody in this country sets the clearance with a #32 bit. If anyone bothers to do it at all, they probably do it guessing and eyeballing what the clearance should be, and the very very few who bother to search for a #32 drill bit might find some charts with the decimal equivalent dimension and determine that "it's close enough to 3mm". Yes, that is true, it is pretty close to 3mm but it isn't 3mm, so setting the clearance using a 3mm drill bit is still wrong. It's pretty close to being right, but it ain't right.
Incidentally, I did check the shift pawl clearance "as found" and it was just a little bit loose, nothing crazy though possibly enough to at least contribute to the problem. Obviously this is a great opportunity to inspect everything I can reasonably look at while I'm in here: it always pays to spend a little extra time to look at and feel as many moving parts as possible, you'll either spot a problem that you can fix, or have peace of mind that all is well down there.
In the next photo, you can see the end of the shift drum minus the detent plate: this makes it easier to see the shift drum pins and the shifter pawl, to the left.
The clearance to be set with the #32 drill bit is between the pins and the pawl. You have to shift into third gear, which aligns a hole in the detent plate with the spot between pins (yellow arrow) and pawl (green arrow), it's a little hard to see in the next photo but it's shown by the double-ended red arrow:
After cleaning the shift mechanism and applying fresh transmission oil, I installed it (as well as the detent plate and a new retaining clip for that) and tightened the new nyloc nuts, by hand only at first. The gearbox must be shifted to third gear. At this point you insert the #32 drill bit's blunt end into the hole and press the pawl down to eliminate the gap (but not so hard that you shift into another gear).
The absolutely important part of the process is to maintain pressure while you tighten the nylocs to the same torque spec of 11N⋅m. I am confident that this is now set correctly on my motorcycle. Of course I also installed a new retaining clip when performing the adjustment:
TO BE CONTINUED...
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