Chainsaw Repair

Aaron I am not up to speed on the different model carbs.   The ones you like what saws do they normally come on and are they larger in venturi size.

The SDC and HS were both made in a multitude of venturi sizes. 

SDC's were used on most of the McCulloch 10-series saws from 54-82cc, Some 103cc and 123cc McCullochs, some 100cc Homelite 1050/1130G saws, many Homelite 58cc SXL-AO and 58cc XL-101 series saws (first saw with an SDC was a Homelite XL-101), and many others.

I've seen Tillotson HS carbs on saws from the 46cc Remington SL-9 (and the larger Remingtons of that design), through the 54/58cc Homelite XL-12/SXL series (first saw with a Tillotson HS was the XL-12), all of the 77/82cc Homelite XL-700/800/900 series, Poulan 200/300 series and 360-451 series 59-74cc saws, all of the 69-85cc 4200-8500 CounterVibes, many 61-99cc Husqvarnas (61-272, 181-288, 285-2101XP, etc), and on and on and on.

I will probably use an SDC or HS from an XL-12 series Homelite or 10-series Mac, as I have a bunch to choose from.  Will let you know the specifics of what I end up using.  The HDB19-1 on a 4000 has a 16.67mm (.656" or so) venturi bore.

Some SDC and HS carbs have a .625" venturi/.750" throttle bore.  Some HS carbs are .687"/.812".  Some larger SDC's are .750"/.812".  Other HS carbs were made in a multitude of venturi and throttle bore sizes for Husqvarna/Jonsered and others. 

There's also more to a carburetor than venturi/throttle bore sizes.  Metering chamber/diaphragm sizes, pump section sizes and configurations, and many other things affect how a carb works with a given engine.  I've found SDC and HS carbs to be much less quirky/touchy than the HDA/HDB carbs.  They're easy to work on and I usually have a multitude of kits for them on hand.  There are versions of both that are suitable for the 3400-4000 application.  Internal impulse passage and an integral idle speed screw are two such items on my checklist.