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Guess it is a common issue and I've read several posts and watched several YouTube videos. V Twin Briggs in a D140 John Deere. I've replaced the carburetor along with new gaskets, fuel pump, fuel filter, air filter. Thought it might be a restriction in the fuel line from the tank so I ran the mower with an auxiliary fuel tank close to the motor. I still need to check the valve lash and governor setting. It doesn't surge under load when the blades are engaged. Please let me know of other things to check as I'm getting frustrated.

Please provide the engine model and type numbers stamped into the valve cover (B&S) or on the label if it is a Kohler engine.

The problem sounds like a blocked or dirty air bleed jet on the carburetor.

M# 44N677
Type 0001G1
Code 150526YG
22 h.p.
I also checked compression/cylinder pressure and both cylinders are right at 120 psi. Carburetor is new but I guess a piece of crud could be in the new carburetor.

The new carburetor could be the issue if it was from Amazon. It is likely not jetted correctly. Do not mess with the governor. The governor only keeps the engine from trying to run wide open and blow itself apart. It is a speed limiting device and it has no effect on what you are experiencing.

In parts tree, this carburetor shows to have regular altitude jets (leaner) and also high-altitude jets (richer). You likely need the high-altitude ones

Not sure what altitude is regular and what is high but I'm in middle Tennessee so.... This was the issue before the carburetor replacement. Regardless, I guess I didn't know different jetting was available for these carburetors.

Surging at low speed is most common with a possible air leak at the intake mounting gaskets, or the air bleed circuit machined into the carburetor. I mentioned the jet difference because that does factor into this problem. This is a Nikki type carburetor design, and they are not known for being the most reliable or easy to work on.

For what it is worth, I would try a second replacement carburetor and see if your luck changes.

I'm gonna pull it back apart tomorrow and see if something has gotten through the new filter and into the new carburetor. I did not mention that immediately after replacing the carburetor, the engine did not surge and ran through the throttle range very well. It was after I'd parked the mower in my shop for a while and then another test drive when the surging began. Thank you for your advice!

These NIKKI style carburetors are not friendly to being opened up and explored without the main sealing gasket being replaced. They swell and distort

Auto Doc's said:

The new carburetor could be the issue if it was from Amazon. It is likely not jetted correctly. Do not mess with the governor. The governor only keeps the engine from trying to run wide open and blow itself apart. It is a speed limiting device and it has no effect on what you are experiencing.

In parts tree, this carburetor shows to have regular altitude jets (leaner) and also high-altitude jets (richer). You likely need the high-altitude ones

Click to expand...

Some aftermarket carburetors run great, except they hunt and surge. They are set up a bit leaner from the factory in China. It can be a very frustrating experience to try to get them to quit hunting and surging. Check to be sure gaskets are in good shape and installed properly and carburetor is tightened down properly.

I am certain the gaskets are in good shape and there are zero air leaks. I am going to check the fuel line from the tank and the in-tank pickup, valve setting and governor setting. After more reading and knowing that the tractor runs ok with a load, I am fairly convinced the idle jet is too small. I watched a YouTube video where a guy gradually increased the idle jet diameter until the surging went away.

It takes a very tiny set of pin drills, and they are easy to break off. (I learned this the first time I tried)

Often times, those tiny jets are just poorly machined and just need to be cleared out using a pin drill bit.

Comparing the original carb idle jet i.d. (.060) and the replacement carb (.025) I've confirmed what several of you have posted. I did drill out the idle jet of the new carb to .060 with a pin vice and drill and the motor ran better but an issue with the needle and seat prevented calling this cycle a success. I bowed to the time crunch and bought an o.e.m. Briggs carb which proved to be the answer. I wanted to take the new Briggs carb apart and measure the idle jet but.....nope. Mower runs very well throughout the throttle range and pulls the blade engaged load very well also. Vast improvement over what it was when I got it. Of course the carb wasn't the only thing this mower needed: Oil/filter change, air filter, fuel filter, new blades, all new deck pulleys, belt and spindles, new drive belt and idlers. Hope the owner/customer takes better care of it this time around. It is stored outside under a cover, not good. Thanks for all the advice!!

Glad you got it figured out.

This is example of just because they claim it fits does not mean that it works correctly. This could likely be used on a smaller displacement engine, and it would actually work due to lower demand on the carb.