Hi, I’ve been running a TM40 for 9 years on my 640 LC4, year 2001. Since it looks kind of crafted with the original trains, I took the one from ner 660 (59002091300) The carburetor was delivered by ABP ready for a 640 without snorkeling.The following setup has the TM40: main nozzle: 137,5 idle nozzle: 20 mixing screw: 0,5-1.0 revolutions nozzle needle: 9D3Y04-96 needle nozzle: Y-6 injection tube: 0,4 idle air nozzle: 1,1 I still have a Sebring Hun Now to the actual topic: the engine runs only with half-drawn choke to some extent ok. Also I mean to hear a slight ringing. I haven’t done anything on the carburettor yet. In my opinion, the 137.5 HD is too small. Should I switch to a 140 HD or larger? How do I set the carburettor best, procedure? Thanks already for hints, Frank