Brand New Walbro Carb... Engine Still Running Rich

[lbeaux]

Hey everyone,

Reaching out to this forum for advice because I just don't have the knowledge to go any further. I purchased a 2020 Cub Cadet XT1 LT50 with around 200 hours on the clock on Facebook marketplace earlier this year. He wasn't asking much for it, and I may have gotten what I paid for. Before I ran the mower, I changed the oil, filter, air filter, and plugs. Originally, the mower would run but ran rough on full throttle - it idled perfectly fine below 50% throttle and I mowed with it several times before getting tired of not being able to run it at full power. I ordered a knockoff chinese carb from Amazon and it ran even worse than previously. I also discovered that there was gas in my oil - I'm assuming this happened while I was turning over the engine many times as I was trying to get the thing to run with the knockoff carb, but I'm not sure.

I ended up ordering a Walbro carb directly from Kohler (or Cub Cadet, either way it's legit) and installed it. I also drained the oil/gas, flushed it with 2 new quarts, and then installed another 2 quarts of oil and a new filter. With the new carb on it runs better than with the Chinese carb, but still not as well as it originally did - originally, I could get it to idle smoothly at low power - now, it runs rich at any power. When running, the engine bucks and smoke comes out the exhaust. The only time it's run normally is when the mower is running out of gas, which lasts for 10 seconds or so. I have also reset the governor, which didn't need much of a reset and I haven't noticed any difference. I've also noticed that my new plugs were black and slightly wet when I pulled them out the other day - I let them dry overnight and attempted to clean them before reinstalling. No difference in operation.

In summary, here are the things I have done to the mower:
-New Walbro carb
-New oil pump
-New plugs (I have removed each while the engine is running to test the other plug, and they are both working, even though dirty)
-New oil and filter
-Governor adjustment

If the carb isn't the issue and the mower is still running rich, what else could my problem be? Thank you SO much for your advice.

Luke

 

[PTmowerMech]

Hey everyone,

Reaching out to this forum for advice because I just don't have the knowledge to go any further. I purchased a 2020 Cub Cadet XT1 LT50 with around 200 hours on the clock on Facebook marketplace earlier this year. He wasn't asking much for it, and I may have gotten what I paid for. Before I ran the mower, I changed the oil, filter, air filter, and plugs. Originally, the mower would run but ran rough on full throttle - it idled perfectly fine below 50% throttle and I mowed with it several times before getting tired of not being able to run it at full power. I ordered a knockoff chinese carb from Amazon and it ran even worse than previously. I also discovered that there was gas in my oil - I'm assuming this happened while I was turning over the engine many times as I was trying to get the thing to run with the knockoff carb, but I'm not sure.

I ended up ordering a Walbro carb directly from Kohler (or Cub Cadet, either way it's legit) and installed it. I also drained the oil/gas, flushed it with 2 new quarts, and then installed another 2 quarts of oil and a new filter. With the new carb on it runs better than with the Chinese carb, but still not as well as it originally did - originally, I could get it to idle smoothly at low power - now, it runs rich at any power. When running, the engine bucks and smoke comes out the exhaust. The only time it's run normally is when the mower is running out of gas, which lasts for 10 seconds or so. I have also reset the governor, which didn't need much of a reset and I haven't noticed any difference. I've also noticed that my new plugs were black and slightly wet when I pulled them out the other day - I let them dry overnight and attempted to clean them before reinstalling. No difference in operation.

In summary, here are the things I have done to the mower:
-New Walbro carb
-New oil pump
-New plugs (I have removed each while the engine is running to test the other plug, and they are both working, even though dirty)
-New oil and filter
-Governor adjustment

If the carb isn't the issue and the mower is still running rich, what else could my problem be? Thank you SO much for your advice.

Luke

What engine do you have on it? Model number is needed.


I assume your choke lever is adjusted correctly. For a engine to run rich, it's getting too much fuel. This can happen when the choke is partially closed or something else is restricting the air. (From air filter to the head). But the needle valve in the carb would have to be open when it's not supposed to be.
Does it smoke when it's at full throttle? And if so, what color is the smoke?

Are both new plugs coated after running it?

 

[Tiger Small Engine]

Before you throw more parts at it, or make more changes, take it to a shop.
When gas got into oil, the needle and seat in new carburetor wasn’t sealing (doesn’t make sense). Why did you buy another Walbro carburetor, when you had the original Walbro carburetor? Check for run condition without air filter on. Check to be sure choke butterfly is fully open when running and off of choke.

 

[lbeaux]

What engine do you have on it? Model number is needed.
View attachment 67041

I assume your choke lever is adjusted correctly. For a engine to run rich, it's getting too much fuel. This can happen when the choke is partially closed or something else is restricting the air. (From air filter to the head). But the needle valve in the carb would have to be open when it's not supposed to be.
Does it smoke when it's at full throttle? And if so, what color is the smoke?

Are both new plugs coated after running it?

PT,

Thanks for your reply.

What engine do you have on it? KT735

I assume your choke lever is adjusted correctly. I believe it is. The choke opens wide, parallel to the ground, when the choke lever is fully engaged.

Does it smoke when it's at full throttle? And if so, what color is the smoke? Yes it does, and it puts out blue smoke indicative of burning oil.
Are both new plugs coated after running it? Yes, both are coated.

 

[lbeaux]

Before you throw more parts at it, or make more changes, take it to a shop.
When gas got into oil, the needle and seat in new carburetor wasn’t sealing (doesn’t make sense). Why did you buy another Walbro carburetor, when you had the original Walbro carburetor? Check for run condition without air filter on. Check to be sure choke butterfly is fully open when running and off of choke.

Hi Tiger,

Thanks for your response here. I agree, the next step is likely the shop. I purchased a new carb at the recommendation of a mechanic. Now wishing I had just repaired the original, but at least I can feel more sure that the carb is not the issue.

 

[PTmowerMech]

I think a compression test is needed.