Over time, especially with darker or thicker eliquids, cartomizers can clog and/or develop a much tighter draw. Here's an inexpensive homemade "tool" that does a good job of clearing the center air tube, without much risk of catching and damaging the coil.
Basically, I just stripped everything off of some spare RG-59/U cable, leaving just the solid center conductor wire exposed. I left a little insulation on the end as a "handle".
I just work it through the carto center slowly and repeatedly, until it's clear.

Basically, I just stripped everything off of some spare RG-59/U cable, leaving just the solid center conductor wire exposed. I left a little insulation on the end as a "handle".
I just work it through the carto center slowly and repeatedly, until it's clear.
