I have two DLE 170's in two 40% planes. They both have the same issue of running rich on low end. When I adjust either one of them to where they have a smooth low end they are so lean they wont start. When I richen them up a bit they start but have that annoying burble I cant stand. The first one I change the carb, ignition, the battery, set the timing to both ends of the slotted spectrum that you are able to adjust but still have that burble. Any thoughts.

A few things to try, gap the plugs to .024, very small adjustments on the low needle. Lean until it takes a short warm up to transition. Try a prop with more load.

drastic fixes. Replace the carb with one just slightly smaller. If the airplane can accomidate, run a canister exhaust system.