Help please.

Hello there, I have a problem with my 89' clipper, it will start and drive totally fine untill in the last couple of days just all of a sudden it will start juddering, the revs will drop and then it will stall, this is at any speed.
I have fitted the usual stuff coil, dizzy+rotor arm, leads and plugs, but no luck.
Any ideas thanks.

crap in your fuel

I did a few things on it yesterday cleaned out the carb with proper carb spray, changed the fuel filter and took the fuel sender out and cleaned the pipes out. It is running mint again now.