Made a thread about it here:
https://www.e-cigarette-forum.com/threads/review-sxk-kayfun-kf-2021-vs-old-v5-and-modifying-it-for-restricted-dl.960893/

edit: mods deleted it because of a troll.

I also have four of them, two 22mm and two 24mm KFL Plus 2021 and converted some of my 2019 versions into 2021 versions.

It's a very good mtl rta but it will feel very tight for most users even with the more open pre-installed air pin. Your solution to cut the pin is good but as you have seen it has it's cons. Removing it completely and replacing it with a silicone plug is the best solution as you have also noted.

All of the accessories for the KFL 2019 including the top fills kits are compatible with the KFL Plus 2021.

Yeah... very good rta. I love it!

I'll be receiving the plugs today... hope that solves the wet 510 issue.

If not, then it's def the space b/n the 510-shaft and surrounding insulator (I've noticed that it's not really that snug/tight. Silicon sealant would def fix that.
But, at least the space b/n the insulator and base's-hole is very tight.

Love my 2019 but it leaks through the 510. Looks like this is no better :(

SirTimmyTimbit wrote:

I've had no leaks through or condensation build up from the 510 pin on any of my KFL 2021 rtas.

djvillan wrote:

Cutting the pin doesn't affect it any differently than not cutting it (leak-wise).

The pin's little o-ring is still in the exact same place. It doesn't press into any sort of flange. It is only side-loaded inside the shaft.

edit: mods deleted my entire ecf thread because of a troll.

Summary:
Using teflon-tape b/n the 510-shaft and surrounding-insulator to make it tight/snug solved the "residual or condensation-build-up on the 510-pin" issue 110%. (silicon sealant would work great too I would think).

Been a couple days chain-vaping the KF2021 now... using 2 different tanks (I use 2 on rotation... my usual deal)... and there is now absolutely ZERO liquid, wet-shine, residue, condensation build-up, liquid smudges/smears at all! Super happy with this tank now!


The silicone plug I initially did first, to replace the oe airflow-pin, did not solve it.
Although the custom plug is very nice, supple, soft, much tighter fit/seal and 20-40x longer than the tiny oe o-ring and seals that 510-shaft 100x better than the little oe airflow-ring, it didn't stop the overall residue on the 510. It was still leaking.
The silicone-plug mod was bone-dry in the center whenever I checked it(a good thing!). But, the outside of the 510-shaft was shiny/wet.... which means it was coming from somewhere else.

This is because I discovered the True source is really from the gap/space b/n the 510-shaft and its' insulator... it is a little loose. (the ID surface of the insulator)

You can try it yourself - unscrew the build-deck/510-shaft-assembly from the tank's base, then hold that build-deck/510-shaft in one hand, and in the other hand slide the insulator over it... you will see you can wiggle the insulator over the 510-shaft a bit.

However... the insulator fitment inside of the base's hole is nice, tight and snug. (the OD surface of the insulator)
In addition, the insulator also has a 90º flange that the 510-shaft's upper-nut presses down on to, when screwing the build-deck back into the base, resulting in an even tighter seal of the insulator's OD surface (no way liquid is making it through that 90º flange). So, this wasn't the source.


In other words:

The main leaking source = the ID surface of the insulator

Not a leaking source = the OD surface of the insulator

Not the main leaking source (maaybe just 1-5% of the leaking, if that) = the airflow-pin's small o-ring (I don't think this is the source; as aforementioned, my long/thick silicone-plug-mod didn't solve it)


Hope this helps!