Hi!
LJCraft 12!
It's probably you low speed needle that is screwed in too far.
I have noticed this many times since I started flying R/C 34 years ago. Just turn it out some and seehow the engine reacts.
And do use the two clunk system (Uni-flow)! It's the next best tank system there is. Only the Tettra "Bubbleless" tanks are better.

To be honest I cannot notice any difference between a one -clunk tank and a two-clunk (Uni-flow)set-up. But I know that the Uni-flow tank system is superior, and as it is so easy to just add one more clunk, I just use that system.

I have used the Uni-flow system in many models through the years and not notice any excess fuel in the silencer! And who cares!
As I always mount my engines on the side, all fuel that eventually runs into the silencer just flows out. But as I said earlier. I have never noticed any fuel coming out from the silencer because of the Uni-flow system.