Newbie on the forum. So I acquired an ’05 S40 Savage 28k bought used from a dealer (dude says he'll never do that again lol). According to him, this thing was reliable up to this year, started stalling, got progressively worse, now won’t stay started if it starts at all. Thus have I rec'd it.

Here is what I have done:

New Raptor petcock
Carb sent in and cleaned rejetted by Carb Shack, rechecked float, jets, etc. Even after, I checked the float etc.
New spark, air filter, oil etc.
New breather hose to airbox
New smaller hoses (fuel, vaccuum, etc.)
Tank - complete cleanout and refill new petrol
New large boots to carb (to engine/airbox)
Recalibrated [valve?’] setting where yo uline up dash to dash on wheel (don’t know what that’s called—crankcase cover area)
Readjusted fuel mixture, idle

Good news: I can take this bike apart and put it back together very fast at this point  
Bad news: Still am at the proverbial square one and I'm not sure what I am misssing here. Now, it'll fire when coaxed, but it'll stall eventually and I cannot take it on the street.

I have been advised to check here on this board--any advice?

’05 S40 Savage 28k
New Raptor petcock
New spark, air filter, oil etc.
New breather hose to airbox
Tank - complete cleanout and refill new petrol
New large boots to carb (to engine/airbox)

People don't have issues with the above  

There can be issues with the following, I encourage you to recheck with the doc's even if you don't think there could be a problem.
New smaller hoses (fuel, vacuum, etc.) --fuel/we don't recommend filters. vacuum, just cap it. vents are open and routed up.
Carb sent in and cleaned rejetted by Carb Shack, rechecked float, jets, etc. Even after, I checked the float etc. --in the tech section (see link below) there's thread called carb specs. check jet numbers, common issue is swapping the main jet with a jet below the diaphragm.
Readjusted fuel mixture, idle --check the number of turns out by counting the number turns in and turning it back out. be careful not to bottom it out hard or it will get stuck

I don't know what you're talking about here.
Recalibrated [valve?’] setting where you line up dash to dash on wheel (don’t know what that’s called—crankcase cover area)

And your buddy could be right. take out the slide diaphragm and check for  cracks and holes.  be careful not to bend the needle.