Carb for 31F777

Hi there I need a carb for a 31F777 engine the carb I have is 2961696179 which is Waldo but cannot find a replacement online could someone help me out at al

Plus one on cleaning vs a Chinese knock off...
 
Here's a link for both style carbs, OEM:
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/200000-399999-series/31f700-to-31f799/31f777-0115-e1/carburetor-kit-carburetor-overhaul 
 
Part #137a, for the Nikki, has a very, very small o-ring that fails and will cause the carb to leak internally and flood the engine.   
 
The Walbro is a MUCH better carb, than the Nikki (IME)
 
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You say it won't start. Will it start if you spray starter fluid down the throat? If yes, your main problem is not the carburetor. That is, you probably need to clean the carburetor, but that's not what's causing the no-start.

 

Figured just a mistake, (I know that you know), just needed to get the OP headed in the right direction.. :)

The carb is still dirty, period.  
 
Did you pull all the jets and spray out the body?
 
A knock off carb should get it running.  

I agree with SRTsFZ6. You think you cleaned it, but the passageways are still blocked. Do like he says. Pull out the jets; take the unit apart and use the nozzle of the carburetor cleaner can to spray into any holes you see (look carefully; some are pretty small). Place the end of the nozzle right against the hole and see if liquid shoots out somewhere else. If it doesn't, something is plugged. Sometimes I pass a fine copper wire into the passageway; I make use of one of the strands that make up common household wire. I also use the air from my compressor to check that the passages are clear; some would argue that that makes it worse, and indeed it would, if the goop in the passage sort of balls together. I don't stop until I've seen fluid blowing out of every single hole! Yes, it takes a little time, but you'll soon learn how carburetors work, and then you can also come to respond to posts like these. Good luck.

There are various reasons for backfire, if it is indeed backfire, that is, fuel explosion at the exhaust. Of course, if fuel can explode at the exhaust, it wasn't completely burned up in the cylinder. And we can divide it into (a) fuel ignited by the heat of the muffler or, on the other hand, (b) fuel ignited by the combustion stroke (the power stroke) where the explosion, so to speak, leaked out the exhaust valve.
 
The former can happen whenever fuel finds its way into the muffler. Maybe there's a fuel leak dribbling onto the muffler, or a poor or intermittent spark (or no spark in one cylinder of a multi-cylinder engine) which leaves unburnt fuel exiting the cylinder into the muffler, or a spark that is so retarded that the fuel is not completely burned by the time the exhaust stroke occurs.
 
The latter can happen whenever the exhaust valve isn't fully closed at the power stroke. Perhaps it's closed enough for some compression and ignition, but as the piston moves down, the valve opens too early and the still-exploding fuel is expelled into the exhaust. How can the valve open too early, you might ask. Well, it's usual that ignition occurs before the piston reaches the top of the compression stroke, and that the exhaust valve starts to open before the piston reaches the bottom of the power stroke. If the timing is off, for instance, the camshaft is not properly aligned with the crankshaft, maybe the exhaust valve starts to open much too soon. Or if the valve lash on the exhaust valve is too tight, the valve will open too soon.
 
So...
 
1) Check for fuel leaks.
2) Is the muffler emitting lots of black smoke?
3) Check for a good spark.
4) Check the key on the flywheel to see whether it split and the flywheel is no longer aligned to the crankshaft. This could be the cause of a greatly retarded spark. Usually, however, when the key breaks, the timing is so far off that the engine won't start at all. Had the motor stopped suddenly in its past, for instance, a mower where the blade hits a big rock?
5) Check the valve lash.
6) Check that the camshaft is aligned to the crankshaft. This is unlikely to be the cause of your problem unless someone opened up the engine and fiddled with the camshaft.