Hi everyone, I'm new to here. I just got confused with my Honda Rebel 250 performance. It has 65k km. First I noticed that both intake manifolds backfire occur in idle. And right exhaust pipe emitting black smoke but left is ok. I remove plugs and checked. Right plug is blacked where I identify as it runs in rich. Left plug is little brown/white colour where I think it runs in fine.i recently replace both intake manifolds boots with a new pair. She has a dual carburator and I cleaned it. what you guys think. ignition problem? Or timing incorrect. Please give me an idea to resolve this. I attached a picture of my carburator. Thanks in advance.