hi i have made the top cover and carb body flat with a emery stone and is very even but it seems to run rich cold it has smoke when you rev engine and it starts witout choke if you start with choke it dies!

but when warmed up the carby seems to be better running like its got no smoke from exhaust!

but when the revs are held you can hear the engine revs go down then sudenly up and at idle its smooth then suddenly it will like sort of bog down then pick up!

could this be a stuck power valve?

should i just buy a new carb from bjprojects for $300?? is it worth it and will it run without any problems then?

Thanks!