Tools
8mm socket
6mm hex key
Slot screw driver bit (2in long) + box wrench
30 gauge magnet wire
Procedure
To access the oil jet cap, first remove the 3 hex bolts to remove the chainguard. Watch out the nylon lock nuts at the other end of the two of the lower bolts - it may falloff. Next remove the clutch slave cylinder by removing two hex bolts.
Note: do not press clutch lever when slave cylinder is detached from the engine.
Here is what it looks like when both the clutch slave cylinder and the spacer between it and the engine are removed. Notice the small pin on the clutch pushrod - don't lose it.
Now you can remove the oil jet cap: you might need a 6mm hex key to do this because it's pretty close to the cylinder.
Once the cap is removed, you can access the oil jet itself. There might be some oil remaining on top of the oil jet - use a tissue paper to remove them so you can see the recess on the oil jet better.
You need a slot screwdriver to remove the oil jet (see the photo of the oil jet below), but forget about regular screw drivers - there is not enough space to use them. I used a long flat screw driver bit (2in long) along with a box wrench. Make sure you press the bit hard against the oil jet to avoid stripping it.
This is a size 30 oil jet, as its marking shows. I used a gauge 30 magnet wire to clean it.
Now install everything back: tighten the oil jet by hand, and install the cap (torque: 15Nm, don't forget the washer).