I used my tektro kit on my tektro brakes today and there was one odd behavior.

When pulling the syringe plunger back out to pull oil back toward the caliper, I got a bunch of pretty much endless bubbles coming out of the slave cylinder body. Some oil too but way too many bubbles.

New bleed kit. Installed and operated according to spec, but it's like air is coming into the cylinder body around the nozzle threads at the syringe. Plunging in works fine (after the oil settles).

I only had the nozzle bolt open 1/4 turn - it was enough for oil to flow thru. The video online showed the guy pushing and pulling the oil thru the system at will. I get these bubbles.

Anyone see this before?

It's very possible the syringe and nozzle aren't fitted properly. Air flows much more easily tna oil, so if there's a tiny leak, the oil won't leak noticeably when you press the plunger, but air will enter, when you withdraw because it's easier for air to enter than oil to flow up the needle when both are drawn by the vacuum.

It's really straightforward. Pull the rubber cap off the nozzle-nut?, slide the hose from the syringe (loaded with oil and hopefully few bubbles) on there, pop open the nut a bit and push fresh oil into the system, which should push bubbles up toward the master cyl where I have another tube attached to catch whatever comes out that end.

When I induce the vacuum, copious bubbles. Does one have to be super smooth with the stroke on the plunger or something like that?

Btw- I'm running chain-L on my MTB and its quiet after 6 rides - needs a frequent wipe but it's quiet! Thanks!

Sounds like you opened the bleed valve on the caliper too far. Air is just gushing around the threads when you apply vac.