debris holding a needle open isn't going to make you spike to 4,000 rpm. you need AIR to match that gas, or you go rich maybe stalling out if it's TOO rich and you flood it.

but, if you have metal everywhere, and the carb is starting to wear out, maybe the butter flies were sticking open because they're worn out?

I see nothing that would jamb open with the linkage you posted pics of.