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Curtis B.
Curtis B., Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 28668
Experience:  Technican turned service manager on multiple lines of equipment and rental equipment.
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My L120 deere mower with a &s 20 hp 2-cylinder engine will

Customer Question

My L120 john deere mower with a b&s 20 hp 2-cylinder engine will start, run, and operate but engine will idle only. I have 380 hrs on engine. The choke works fine and will increase engine rpm before engine sputters. All mechanical carb linkage is connected, intact, and working fine. Everything is fine, I just can't increase engine rpm with throttle control after starting? It's been running fine all summer.
Submitted: 1 year ago.
Category: Agriculture and Farm Equipment
Expert:  Curtis B. replied 1 year ago.

Is the fuel solenoid in the carburetor moving full travel? If it does not retract , it can block the main jet to the cylinders.

Expert:  Curtis B. replied 1 year ago.

Best test is to remove it, and plug the hole for test.

Customer: replied 1 year ago.
I can't tell if the solenoid is retracting. Do I have to remove the carburetor to remove the fuel solenoid?
Expert:  Curtis B. replied 1 year ago.

No, it screws out, it just takes a thin wrench to get to the hex.

Customer: replied 1 year ago.
Thanks, ***** ***** the solenoid and let you know how I make out. Thanks.
Expert:  Curtis B. replied 1 year ago.

Ok, thanks, ***** ***** it , you also will drain the float bowl on the carburetor, and will let let any water or debris.

Customer: replied 1 year ago.
Curtis, I'd like to report good news but no such luck. I removed the fuel solenoid his morning and its works fine. A little dirt in the bowl so I cleaned the solenoid with carb cleaner and energized it a dozen times and it worked every time. Put it back on and had the same problem, engine starts and idles only. I took the top cowling off the engine and disconnected the throttle linkage to the carb. I started the motor and manually rotated the carb lever, nothing, only idle. I'm not a carb man and don't know what's inside, where do I go from here??
Expert:  Curtis B. replied 1 year ago.

The throttle lever attaches to the throttle shaft, which moves a butterfly valve in the carburetor. See if the butterfly is moving when you manually move the throttle lever, do this with engine OFF. I have seen throttle shaft broken, and butterfly not moving.

Expert:  Curtis B. replied 1 year ago.

Here are the two parts of the carburetor breakdown,

Customer: replied 1 year ago.
Thanks Curtis, difficult to see the butterflies because of the high plastic intake manifold. With the aid of a small mirror, I could see the butterflies attached and moving freely when I rotated the throttle lever. Could the problem be a bad fuel pump or dirt in my fuel filter??
Expert:  Curtis B. replied 1 year ago.

Remove fuel line at the carburetor and crank to see if you have fuel to carb.

Expert:  Curtis B. replied 1 year ago.

If no fuel, then check backwards

Customer: replied 1 year ago.
Thanks, ***** ***** fuel filter since it was quick and easy. I disconnected the fuel line at the top of the carb and cranked engine, fuel pump was pumping gas. I started engine and it just idles. Runs strong, choke side of carb works, but throttle lever on left side will not increase engine rpm.
Expert:  Curtis B. replied 1 year ago.

I know you think i'm crazy, but can you remove the solenoid and plug the hole for test. You can plug it with cork, wooden plug , just anything, for short test. it has to be at the carburetor. Or if it is not the solenoid, maybe the two jets in the base of carb may have fallen out!

Customer: replied 1 year ago.
Curtis, I had a power failure last night and cannot open your last two responses, can you resend them? I believe from the cover page that you are asking me to remove the solenoid and start the engine, correct?
Expert:  Curtis B. replied 1 year ago.

I know you think i'm crazy, but can you remove the solenoid and plug the hole for test. You can plug it with cork, wooden plug , just anything, for short test. it has to be at the carburetor. Or if it is not the solenoid, maybe the two jets in the base of carb may have fallen out!

Expert:  Curtis B. replied 1 year ago.

Yes, remove and plug hols to see if it will run.

Customer: replied 1 year ago.
Curtis, I pulled the solenoid, plugged the hole with a small cork and started the engine, no change. Starts right up but will not increase rpm with throttle linkage. While I was there, I removed the muffler cover under the carb and linkage area to give everything another good inspection; all linkage is attached, two springs are in place and connected properly, governor lever ok with locking hardware tight. I just used the mower for the last hour or two cutting the grass by increasing rpm with choke and operating rpm at about 60%. Not pretty but got the job done.
Question, if everything is connected properly and butterflies are moving freely, with motor running, why is there not change in the engines noise, rpm, etc. when I move the throttle. Nothing happens.
Expert:  Curtis B. replied 1 year ago.

Your choke is part of the throttle cable? At full throw, it activates the choke? Or is choke cable separate. Look at the picture, in link above. The clips with blue inked on both cables, is what controls the throttle and choke throw. Could your throttle cable have slipped under the clip? It may need to be adjusted, so the cable pulls further?

Customer: replied 1 year ago.
This is exactly what I have except my solenoid hangs down vertically on the bottom of the bowl. The lower cable runs to my choke lever and the upper cable runs to my throttle lever. I don't believe anything moved under a clip but I will check tightness in the morning. Thanks.
Expert:  Curtis B. replied 1 year ago.

Try moving the top cable, loosen the clamp and work cable by hand.

Customer: replied 1 year ago.
I removed the throttle cable locking clip, started the engine, and moved the cable manually. Nothing changed, same issue. I've attached a few pics.
Customer: replied 1 year ago.
Another pic
Expert:  Curtis B. replied 1 year ago.

Have you taken the carburetor off and checked the two jets in it? That seems to be the next step, as it does not seem to be external.

Customer: replied 1 year ago.
No, I'm a little reluctant to remove the carb without a rebuild kit, or at least a new gasket kit. Since the engine starts and runs, is there any way I can get a cleaning agent in the carb, adding something in the gas, or spraying something in the carb? Thanks
Expert:  Curtis B. replied 1 year ago.

I don't see this as something that a carburetor cleaner in the fuel , or spraying in carb, is going to help! I see this as a mechanical failure.