I used this awesome guide today to fix my HH. The button had come off. I was able to find the red/slotted gear tooth by using a bore scope camera pointed at the gear, and then momentarily pressing the starter. It took about 15 tries to get it to the right place. I found it three times in kind of the wrong place, and then I had it pretty much right. The "scored/red" gear tooth actually has a slot or groove that goes vertically None of the other teeth have the groove in the end of the tooth. I guess I could make a little ascii art... I guess this is what it would look like from above or below.
/ \ Regular tooth.
/-\ Slotted tooth.
Next, from the side looking in the fuel cutoff window each tooth looks normal except the slotted one which has a groove down the middle. The xx in this diagram is the space in between each gear tooth.
| |xx| |xx||||xx| |xx| |
............^---------------------Slotted gear tooth.
.^----^----------^----^---------Regular gear teeth.
The red paint/indicator seems to be painted into the slot.
It seems like to get it apart, you must line it up, and then remove the head (the fuel cut off lever must come out for the HH to come off.) I'm not sure how you time it if you're putting it together for the first time, but I did see a you tube video about a complete pump rebuild where the guy went over every detail about putting a pump back in. Also when you're putting the head back on, you have to push down on the head and slightly compress the spring to get the fuel cut off lever to go back in. The fuel cut off actuator has a little square pin that slots into a groove. Oh also, there *is* a groove that the little clip for the fuel cutoff lever goes into. You kind of have to hold the arm thingy out, and snap the retaining ring in. Its definitely one of those 'I *really* hope I'm not going to drop this clip' situations.
-Zoey