C-85 Backfire?

John, when my poor bird sat for 7 months when I was sick it did the same thing. I checked around the intake hoses for cracks and blue stains, but no joy. A common cause of backfiring is an intake leak. I don’t have my logbook handy, but I had a variety of problems, like a broken exhaust stud with a loose exhaust and other stuff I can’t remember. I think there was an intake leak, but there was more than that. How did all that happen sitting in the hangar? Heck if I know!

I haven’t flown my plane much since I got sick last July. I usually fly way more than 100 hours a year, so it’s weird my little Ercoupe had to sit neglected for months.
The old girl surprised me by staying in great shape and even the battery stayed charged. It passed its annual with flying colors, too. 
Her engine is a C-85 with the O-200 crankshaft STC. 
I have noticed, though, a little popping when throttling to idle with a warm engine. I’ve had real backfiring in the past when I had an intake leak, and these new ones are much quieter. 
i checked the intake hose clamps and made sure they were snug. There were no blue stains, so I assume that’s not my problem this time. 
I’m thinking that the long time sitting may now be causing the valves to stick just a little bit. 
I plan to put a cup of MMO in the oil and then give it a good long run next Wednesday to eat BBQ at Hot Springs. 
Any thoughts?