Briggs 16HP Vanguard carb / fuel problem

[Forest#2]

You need to put the air shroud back on that engine. (before you overheat and ruin the engine. The air shroud no longer needs to be off.

Have you had the main jet out of that carb? (and the emulsion tube that is normally connected to the main jet?
If so, did you look at the emulsion tube carefully and rod out all the itty bitty cross drilled holes in the emulsion tube????Some are really small and hard to see if the tube is dull colored.
Does the engine set and idle good and smooth?

We can get into the static governor adjustments later.
It's still starving for fuel or getting too much air. (due to a leaking intake manifold behind the carb. Have you had the manifold off and installed/checked new seals where the manifold bolt to the heads and make sure the plastic manifold is not cracked???
In your post number 18 that gasket is bad and also appears to be installed wrong between the carb and the intake? Have you replaced that gasket and did you get it installed correctly?

 

[Wurzel]

Yes the main jet and emulsion tube above have been out a few times and thoroughly checked, including the cross drilled holes in the tube body. I can't find any leak around any manifold mating surfaces or seams by using carb cleaner. I will swap the gaskets between carb / manifold adapter / manifold for good measure. Is either a case of too little fuel or too much air, there's nothing to say the main jet is original, but it's clutching at straws. I also changed the fuel lines between filter / pump and valve cover / pump as they had surface cracks. Engine does settle into a steady idle and doesn't hang. The only thing I haven't tried is giving it some ether at the carb when it starts to stumble, the result is predictable but I'll confirm nonetheless.

 

[TobyU]

Yes the main jet and emulsion tube above have been out a few times and thoroughly checked, including the cross drilled holes in the tube body. I can't find any leak around any manifold mating surfaces or seams by using carb cleaner. I will swap the gaskets between carb / manifold adapter / manifold for good measure. Is either a case of too little fuel or too much air, there's nothing to say the main jet is original, but it's clutching at straws. I also changed the fuel lines between filter / pump and valve cover / pump as they had surface cracks. Engine does settle into a steady idle and doesn't hang. The only thing I haven't tried is giving it some ether at the carb when it starts to stumble, the result is predictable but I'll confirm nonetheless.

I am certain you're going to find if you give it some extra fuel, I would use gas and a spray bottle or card cleaner and not starting fluid because that's way hard on an...that you will find it will not lean out like that and keep the throttle plate wide open and start to die.
I can see in the video that the throttle is going from the minimum idle setting all the way to wide open from the governor as soon as it runs out of fuel.

So if it's not the jet clogged up or way too small of a jet opening from being the wrong jet which I doubt is the case but it is possible, my next thought would be not enough fuel in the bowl.

This doesn't happen very often but it certainly can.
It can be from the fuel pump or fuel lines not supply enough fuel like what I fuel line degrades inside and swells up and pinches itself off so instead of being a nice flow it's just a trickle.

I think the fastest way to test this in your case would be to remove the fuel line from the carb and not do the normal crank the engine or run it over and watch it spurt out of the line for the fuel pump which that would be something I would still probably do but I would go ahead and get a new piece of short fuel line and a small gas tank or some other way to provide fuel to it and just hold that tank in your hand as gravity fed and then let it run to see if it runs normally or still does the exact same thing.

If it acts the same way then I would suspect the inlet valve of the carburetor.
I think that carburetor will have the needle valve with the rubber tip and those don't usually cause restrictions but the push mower style Briggs with the rubber seats up inside the hole like the Tecumseh often swell up and the hole gets so small they only trickle when they should flow much greater.
And either way, there can also be something clogging it up as I found three brand new Chinese engines on riders and just two seasons that had some sort of cloth wadding packed into that inlet from the fuel line that was restricting flow greatly.

If a gravity fed plentiful fuel source doesn't straighten it out for test purposes I would remove the bowl, float and needle valve and blow a strong air pressure backwards through the needle valve letting it blow the air out of the carburetor fuel line inlet nipple.
I have had some so bad I've had to run a wire or a pipe cleaner through that passageway.

I just think you have to be leaning out and starving for fuel and these are the most common ways that happens.
Some other rare occasions are when the float is wrong or something is rubbing inside and it can't move freely or far enough.

 

[Forest#2]

Right:
AS TobyU says bypass the existing pump fuel system by rigging up a gravity feed tank.

If you do not have a tank as such:
I have as a quick bypass of existing fuel systems is rig up a vertical piece of 1/4 inch or 5/16 tubing about 3 ft long, (tire the fuel so it will stand up vertically as gravity feed to the carb take a small funnel and fill the tubing with gas, then start the engine and go to full throttle immediately. The engine should run good for about 60 sec or more just using the gas in the tubing plus the full bowl of the carb gas.
If that works ok, think about getting a regular USA LMT carb or even roll the dice and install a clone nikki. Your carb and governor linkages will have to re-arranged. to the USA style but rhose can even be made using survey flag wire. (your existing LMT carb and linkages linkages are of the un-usuall type is mainly why you are stuck for now with that carb and we do not know for sure if it's the carb, but all now is pointing to a carb that is leaning out for some reason????????????

 

[Wurzel]

Thanks both. We have previously tested for good flow at the carb inlet, but not the passage between the inlet and bowl / main jet. I've had the float valve apart but can't recall what tip it has or what it seats in. I'm pretty sure I blew it all through previously in the initial carb cleans, but there could still be a restriction there. In any case I'll do it again and also with a temp fuel supply which I can rig up fairly easily.

 

[Forest#2]

Just curious.
Are you located in the USA?

The reason I ask is you say that carb is Asian and that is not a standard Walbro LMT throttle and choke linkage set-up is not normal for a USA Briggs twin?
(Some of that re-branded equipment (has a JD name but parts and pieces made by others for JD) has some strange rigging sometimes. Frankenstein type equipment maybe)

 

[TobyU]

Just curious.
Are you located in the USA?

The reason I ask is you say that carb is Asian and that is not a standard Walbro LMT throttle and choke linkage set-up is not normal for a USA Briggs twin?
(Some of that re-branded equipment (has a JD name but parts and pieces made by others for JD) has some strange rigging sometimes. Frankenstein type equipment maybe)

I couldn't see much of the engine in the video but it kind of looks like one of the older horizontally opposed twins to me.
I think I could see an aluminum crossover intake.

 

[Wurzel]

Just curious.
Are you located in the USA?

The reason I ask is you say that carb is Asian and that is not a standard Walbro LMT throttle and choke linkage set-up is not normal for a USA Briggs twin?
(Some of that re-branded equipment (has a JD name but parts and pieces made by others for JD) has some strange rigging sometimes. Frankenstein type equipment maybe)

UK, note its an 'Aisan' not 'Asian' carb

 

[Wurzel]

I couldn't see much of the engine in the video but it kind of looks like one of the older horizontally opposed twins to me.
I think I could see an aluminum crossover intake.

Yes aluminium crossover intake

 

[slomo]

Governor is working as normal. Move along. Your video shows it clear as day.

Looks like the pilot circuit runs out of fuel and hits on the governor for more gas from the main jet. Indicates fuel delivery issue and or clogged carb. Vacuum leaks??????

Dump fuel tank out and flush with fresh fuel. Make sure the tank inside is spotless. All new fuel lines from tank to carb.

Pull fuel hose off at carb inlet. Should drain the tank with a solid flow AT the carb. Drain gas into a glass jar. Pour back in the tank through a coffee filter.

No reason to be on 8 pages now and still have a hunting/surging engine. OP has missed something or ignored/missed some advice.