It's the pilot screw:

On some carbs, it's sealed and not adjustable. Consider it as a bonus that you can fully remove it and clean it as needed on that new aftermarket carb.

 

goooood luck

 

That controls air flow through the pilot jet.

 

Chinese Huayi Carburetor Factory carbs are actually considered "genuine original", and not aftermarket, as they are found stock on almost all OHV blowers, in contrast to hundreds of jobber nameless carbs which are copies of Huayi Carburetor Factory carbs.

The OP upgraded to a better carb

How times have changed.

 

The snowblower started first pull after installing the new carburetor shown in the OP and fuel filter. I'm slightly disappointed that the engine requires half choke to run....

I didn't take enough pictures beforehand (sigh), but I'm not positive that I routed the fuel line from the tank to the fuel valve exactly how it was before I operated on the machine. Not sure how critical it is the line to always having downward slope from the tank to the valve is (or if it could result in the machine running lean).

Since the replacement carb was brand new, I didn't take it apart and check for debris before installing. Did I make another mistake in not checking / cleaning the new carb?

Would replacing the main jet with a slightly larger orifice correct this issue? I'm not even sure what jet size the carburetor came with....

Any advice would be welcome. Should I start a new thread? Thanks everyone!

 

Would replacing the main jet with a slightly larger orifice correct this issue?

Yes, most likely. You could remove the pilot & main jets from the original carburetor, thoroughly clean them and see if they improve the operation on the new carburetor.

 

I'm not even sure what jet size the carburetor came with....

The main jets are often stamped with the sizes. You should check since you now have a spare carb (the original):

If you don't have one already, invest in a micro drill bit kit.

Amazon.com

Have you tried fiddling with the pilot screw on the new carb, (since it's adjustable)?

 

I haven't tried making any adjustments yet. I'm trying to best understand the problem and how the different inputs work on the carburetor before I start "turning dials". Also, this is my best friend/neighbor's machine and I would feel bad if I somehow made it worse.

At a very high level, it appears that the carburetor is not receiving enough fuel. I've read on this site, to remove the carburetor bowl, open the fuel valve, and observe the flow rate of the gas, but I have no idea, what the expected flow rate should look like. Although, it does make sense to start at the fuel tank and systematically work my way to the engine.

The main jets are often stamped with the sizes. You should check since you now have a spare carb (the original):

View attachment 222804


If you don't have one already, invest in a micro drill bit kit.

http://[URL]https://www.amazon.com/...s=micro+drill+bit+kit&qid=1705954281&sprefix=micro+drill+bit+kit,aps,98&sr=8-32

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Have you tried fiddling with the pilot screw on the new carb, (since it's adjustable)?

 

It's a gravity-fed fuel system, so it should be a steady stream, like water flowing through a 1/4" hole but at a slightly faster rate, as gasoline has lower viscosity than water at room temperature: 1 cP for water versus .4 to .5 cP for gasoline.

Without choke, if it surges while it's running at high speed+without a load (meaning, the throttle lever is in the rabbit position+the augers are not turning), does it also surge when you squeeze the auger lever?

If it stops surging when the auger lever is engaged, then likely culprit is that the idle jet circuit is either plugged up, or that the idle jet is too small from the factory.

If it surges with and without a load, then perhaps you'd need to enlarge both jets.

Here's a video of enlarging the idle jet:

 

I'll record a video of the machine running this weekend and post. My memory of it running this past Sunday was that it wasn't surging (at low or high rpm's with it without auger load). The engine would die if less than half choke was applied.

The dialog we're having really makes me want to check the fuel flow to the carb...

 

Your new is a Huayi and the old is a Ruiing. Both are used as OEM and both are good carburetors. I prefer the Huayi. I think the jet should swap between the two.
When looking for a replacement carburetor, I will buy the one with the manufacture name cast into it. The cheap, cheap ones will not have the name cast into them and I am more dubious of quality.
A lot of the available replacement carburetors are jetted for summer time power equipment / EPA lean and need re-jetted for winter

 

Another reason why I don't like carbs made in the amazons.

They are often advertised for 'go karts' and may have diferent sized jets.

These carbs have no jet screws, they are determined by the size of the jet parts themselves on assembly.

 

It's actually Ruixing (the star on the logo is supposed to represent an X), everything else you wrote is spot-on.