Briggs 15HP PowerBuilt engine surging(I’ve tried everything!)

[Hathaway’s S.E.R.]

The logic behind holding the governor is to eliminate it surging so you can hear what the engine is actually doing.
So you start the engine then slowly increase the throttle opening.
At some point in time the engine will start to faulter.
As you do engine repairs how it starts to faulter should point you in the right direction.
Surging is nearly always a lean running condition.
It could be something as odd as the stud hole for the manifold penetrating the inlet tract.
While the engine is faultering saturate the manifold region with WD 40 from a trigger pack using your other hand
Do little bits at a time so you can find where the air leak is , assuming there is an air leak.

Have you tried the alternative tank yet ?

Alternative tank did nothing, i tried WD-40 all around the intake and couldn’t find any leaks. Also tried brake cleaner to see if the engine would race and nothing.

 

[bertsmobile1]

How did you go with manually opening the throttle slowly till it faultered ?
You are really only left with things like a leak around the inlet guide or a cracked head