Toro Push Mower Engine Revs Up and Down

[bertsmobile1]

IF you installed the carb with the seat not fully home so the float is not sitting horizontal the fuel level in the bowl will be too low so the engine will surge when running on the man jet
The hole that the red rubber seat goes into is not strait
Down the very bottom there is slightly smaller diameter section to hold the seat tight I think your seat is sitting on it and not in it
A touch of silicon spray goes a long way to getting it to seat properly
DO NOT USE WD40 beause it will make the rubber go soft

 

[tim the pacesetter]

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 ei

 

[slomo]

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

Both videos don't load for me. I'm not a googal user at all. Like to keep all my useless personal info to my useless personal self.

 

[tim the pacesetter]

Thanks, guys. I was sure to clean the carb really well; including every small hole I could find. Used carburetor cleaner, very thin needles, air pressure spray, etc.

One thing that I wanted to do was remove the emulsion tube. However, I was unsuccessful with that. Does anyone know how to remove it? I'm not sure where the holes are, though. I could enter it
from the top with a thin needle to try to loosen up what's in there but I don't think that's what I should be after - just going in from the top.

About the seat, I really made sure it was seated well. I appreciate all the tips, guys. Thanks Slomo for mentioning the nut that fastens the bowl. I and already tightened it, though- hopefully not too much.

Something tells me I might end up taking the lawnmower to the shop because things are getting pretty technical.

 

[slomo]

I might end up taking the lawnmower to the shop because things are getting pretty technical.

I don't think so. You've done most of it yourself, already.

Reach inside the carb throat. The emulsion tube - if your carb has one - can be removed but pushing down in the center of the throat. You should see a brass tube barely protruding from the floor of the carb throat.

After looking at your carb again, I can't see an emulsion tube. Unless the other REAL experts can confirm you have one or not.

IF your carb has a pilot circuit, it might be under this welch plug. Look at the center of the pic. See that round area with the round cover plate? That's the welch plug or looks similar to one. See the only visible carb mounting bolt? That bolt covers the lower right portion of the plug.

 

[tim the pacesetter]

Thanks, Slomo. I'm not good knowing the technical parts yet, but you know when you look into the carb and there is a brass disc that's bigger than a dime yet smaller than a nickel, and it rotates? There's a tube running through that (top to bottom - or bottom to top). I'll look into this when I get at the carb again.

Check this out, though. I think I may be on to something here. About an hour ago I removed the carb to set the float parallel. I managed to do it successfully with heat (see pic below). But when I reinstalled it and started the mower, the mower went back to square one - the surging was as bad as the beginning (see before video). Talk about annoying. BUT, just as I sat down to write this post, I realized that I forgot to reattach the crankcase breather tube (see pic below. This image is not of my mower. It's from the outdoorpowerinfo page).

Could this breather tube have been the culprit all along? I noticed the first time around that the end of the tube that connects to the engine is pretty loose and kind of wants to slide off. I'll order one today and see how things go after I install it.

 

[bertsmobile1]

Heating the float & bending is the wrong way to go.
The red rubber seat is not down fully
You have to push them down quite hard to get past the little step at the bottom of the hole
So your fuel level will still be too low

 

[tim the pacesetter]

Thanks. What's strange is that the float wasn't parallel the first time I opened the carb (bowl).

Regarding the red seat, I really pressed down firmly with the end of an allen wrench with the same diameter as the seat "washer". Did this twice. Any harder and I was going to break something.

 

[slomo]

Thanks, Slomo. I'm not good knowing the technical parts yet, but you know when you look into the carb and there is a brass disc that's bigger than a dime yet smaller than a nickel, and it rotates? There's a tube running through that (top to bottom - or bottom to top). I'll look into this when I get at the carb again.

That is your throttle plate. Regulates air flow into the carb.

 

[slomo]

Could this breather tube have been the culprit all along?

Not normally. Just ad a zip tie or order new as you mentioned.

Float level looks good to me now. Use silicone spray next time when installing the red seat.

You need to look behind that round welch plug. SAVE the round plug cause you will need to reinstall or order new if available. If you reinstall, you will need to reseal the round plug.

Words of caution. Don't throw away any Briggs or other brand mower parts. Some of these older Briggs engines, parts are gone.

You might need to boil the carb a couple times. Bertsmobile1 has a great method he uses. Might ask him about it.