D140 Surging

[67Camaro]

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.

 

[Auto Doc's]

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.

 

[67Camaro]

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.

 

[Auto Doc's]

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

 

[67Camaro]

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.

 

[Auto Doc's]

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.

 

[67Camaro]

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!

 

[Auto Doc's]

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

 

[Tiger Small Engine]

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

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.

 

[67Camaro]

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.