Viper 150 carb advice

[Britt]

I've got a new Viper/Hawk 150, and I'm having trouble getting it to idle reliably. (Though it seems to run OK when not being forced to just idle.) Sometimes it will idle fine, albeit a little fast, and other times it will just die out, either immediately or after an undetermined amount of time. Yes, it pops a bit on deceleration when I just rev it. Granted, I've only got a couple hours on the bike thus far, if that matters.

The carb is a PZ27. I have access to the Idle Speed Screw in the middle on the side, but the Idle Mixture Screw is not exposed, and the hole it should extend from (on the underneath of the carb on the engine side) seems to have some type of black resin/glue/epoxy inside it.
If the carb is not easily tunable (the seemingly plugged Idle Mixture Screw, and it's my understanding it isn't easy to find jets for the PZ27), can anyone recommend a decent tunable carb and/or advice on how to make tunable the one I have and where to find appropriate jets? Or would I be best off by just buying another cheap PZ27 that actually has an adjustable Idle Mixture Screw?

I don't have any real carb experience, just a PZ Tuning Manual I found from Walbro that covers the PZ26--yes, the PZ26 rather than the PZ27, but they look identical.
Thanks in advance for any advice!