Toro Push Mower Engine Revs Up and Down

[tim the pacesetter]

Awesome, thanks Slomo. I appreciate these steps you outlined. Also, thanks for pointing out that this mower is a keeper. This is good to hear.

 

[tim the pacesetter]

Hi guys. Thanks for all your help. The Carb rebuild kit arrived today for my lawnmower. Toro Model 20038 (Briggs and Stratton engine Model 122602-0111-E1).

I'm having a hard time finding rebuild directions. I visited the link Bert sent but its hard pin-pointing which instructions pertain to the model I have. Could someone help me zero in on the right instructions?

Below are some images of my lawnmower's carburetor. Images will expand if you click on them.

This is the page Bert referred me to. My carb is probably right on that page but I'm having a hard time figuring out which one.

https://outdoorpowerinfo.com/repairs/#id_briggs

 

[bertsmobile1]

this one
Then click the link on the bottom that says Disassembling Briggs carb 790120 for cleaning

 

[tim the pacesetter]

Thanks Bert. I appreciate this. I'll be sure to come back and let you know how it goes.

 

[tim the pacesetter]

Hi guys. I'm in the middle of my rebuild but have come across a problem I'd like to run by you. I'm having a hard time getting the carb float to rest parallel to the carb.

I replaced the red "seat" and made sure it was down all the way (used the butt end of an allen wrench to firmly press down on it - did this twice). But the float still rests in the air a bit. Does anyone have an idea on how I can fix this?

 

[slomo]

Yours looks right but confirm the seat is installed proper.

"This carb uses a replaceable rubber seat, visible in red in #7. A new seat is installed with the grooved side in first, away from view. The needle mates with the chamfered hole of the seat, which faces outward".

The float height CAN be raised or lowered. Need a little heat on the plastic tab that pushes on the needle. Be gentle with the heat.

Float height should be parallel with the carb body, where the float bowl mounts to and seals. Turn the carb upside down. Look at it with a level, inverted carb body. YOURS looks too low. Float needs to go DOWN towards the carb body and bowl sealing area. Just a little bit. Again easy on the heat.

Don't try to bend that tab or it could break off.

 

[tim the pacesetter]

Thanks. I did install the red seat with the grooved side in first, away from view. It has a grooved right around the perimeter of it. What does chamfered hole mean?

 

[slomo]

It's where the fuel goes into the carb.

 

[tim the pacesetter]

Got it, thanks!

I installed the rebuilt carb a short time ago and it started on the second pull. However, I can still hear the up and down revving somewhat. Could this be another issue?

If you have a moment you can watch the 10 second before and after videos.

Before:

Toro Carb before.mp4

drive.google.com

After:

Toro carb after.mp4

drive.google.com

 

[slomo]

Surging again, is most lilkely a dirty carb or fuel delivery issue, gas cap vent or fuel hose. Could be a vacuum leak as well.

Your carb has a low speed or pilot circuit it uses to start and run the engine at low revs. THIS little fella' has tiny jet holes. Might be covered with a flat, round shaped welch plug on the carb body. Have to remove the plug to access the jet. Also the emulsion tube on top of the main high speed jet has tiny holes that needs to be open.

Remember the carb body is aluminum. Both jets are soft brass. Be careful not to over torque the fuel bowl cup and jets ect..... All you need is a GENTLE snug. Turn with your off hand until the screw stops turning only. Most people are right handed so use your left hand. Why, that hand is not as strong as your main hand. Don't need any impact guns either.