So I don't come on here much these days, as I mentioned to someone once I only really frequent the forums when I have a problem with my bike.
Well, I'm here aren't I?
Problem: When rolling on to 2nd gear, there is a skipping/mechanical hell sound that sounds like a skipping chain, sounds like the motor is about to eat itself, and the bike hesitates and chokes and doesn't like it.

This doesn't happen: In any other gear than 2nd, and if I roll on veeerrrry verrrry slowly into 2nd gear. It'll still do it if I'm not careful.
Recently: replaced the chain - this was happening before that - and replaced the plugs - again, this was happening before that, too.
What are my likely problems here? I have been commuting on the bike and skipping 2nd gear completely out of fear. Are my carbs just sync'd like @$$ or is this more likely a mechanical issue (i.e. transmission-related, bad sprocket, bad ????)?
I'll try to get a video of it happening, but I've been busy lately so instead of being able to deal with it, I've pretty much parked the bike.
Thanks y'all