Hi BT, you didnt say how much runtime you have on this engine?
Do you fly off a grass field and maybe over time the carb has sucked up specks of debris and some dirt, causing the compression to get lower over time. If you have lots of runtime on this engine, maybe a new piston ring is in order? You may also want to check out the YS engine section here on RCU, Troy Newman is the moderator there and he is the GURU and a great guy too for asking advice.
Keep us posted on what you find