Chris, the crankshaft doesn't really know what stroke it is on. The piston is either up or down or somewhere in between. What constitutes one of the 4 cycles is how the cam timing is affecting the valve
First, you need to get a rebuild kit for the carb. Also, if your carb is leaking like that, your petcock is probably leaking also, so you would need to replace it. Remove the carb and take the bowl off
Kirby, about the only source of "black bits" inside the motor would be shown here: http://www.cmsnl.com/honda-ct90-trail-90-k0-us_model619/partslist/E++04.html The camchain tensioner/guide rollers
You will need to replace the seals as well. Have the bike sitting on a stand so there is no pressure on the forks. Remove the tire, fender and brake caliber. Drain the oil. You will see a screw on the
Not really sure why they told you that. That bearing is not different than any other big bike. They all use the same bearing. If you look at the v-twin manufacturing on-line catalog on page 386 they do

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