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Toro Push Mower Engine Revs Up and Down

#1

T

tim the pacesetter

Hi folks. My lawnmower revs up and down when try to use it. I think this might be called, "hunting and surging". The mower is about 10-15 years old.

I made a 10-second video and I'm hoping someone can view it and offer possible solutions.

Video Link:

drive.google.com

Toro Carb before.mp4

drive.google.com drive.google.com


tlm.jpg


#2

M

mechanic mark

Order a carburetor rebuild kit using numbers & manufacturer of your engine. Remove carburetor & disassemble completely & use an ultrasonic cleaner or just google how to properly clean a carburetor before rebuilding.


#3

T

tim the pacesetter

Thanks, Mark. I'll look into carburetor rebuild kits and cleaning methods. I appreciate your help.


#4

B

bertsmobile1

Step by step instruction with good photos are found on the out door power info site


#5

T

tim the pacesetter

Thanks, Bert. I visited the site but when I searched for my Toro model number (20038) it didn't yield any results. From what I understand, it has a Briggs & Stratton engine. I'm wondering if I should check the engine for its own model number. I'm a few miles away from the mower location so I can't go look at it at the moment.


#6

B

bertsmobile1

Yes check by engine make & model not by what it is fitted into
The carbs are all the same regardless os who is fitting them


#7

T

tim the pacesetter

Thanks, Bert. I appreciate your help and for providing the outdoor power info link. Personally, I'd go straight for the rebuild. However, I have a relative that wants to install a new, non-OEM product. I'll wait until this $10 new carb bombs and then do the rebuild :)


#8

S

slomo

That mower is definitely a keeper. Do what you can to get her running. Hard to find a better mulcher than that one. THAT was back when Toro made good pushers.

Definitely a dirty carb or fuel tank issue. Something is limiting fuel flow.

Remove fuel tank and flush it out.

Install new fuel line. Filter and a shutoff valve are good ideas too. Cheap also.

Like others said clean and rebuild the OEM carb. Don't go to ebay or amazon looking for Chinese carbs.


#9

T

tim the pacesetter

Thanks, Slomo. I'll start with the carburetor first, and maybe move on to the other maintenance. I'm glad to hear this mower is a keeper. I'll take of it for sure.


#10

S

slomo

On a mower that old I would do:

1.Clean and rebuild the OEM carb. This is your most likely issue. Also check for vacuum leaks.
2.Flush fuel tank and install new fuel line and filter if you have room.
3.Pull the head and de-carbonize the cylinder, head and valves. This is in your engine manual you need to download.
4.Remove the metal engine fan shroud. Clean the top, bottom and all around the block. Remove all grass, dirt, oil and bugs from the cooling fins. Clean the entire engine like it was new. As Bert said, there is clean and then there is CLEAN. Look behind the muffler and such. Go all CSI on her. This procedure is also a must do, in your engine manual.
5.While you have the head off, check valve clearance.


#11

T

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.


#12

T

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.

Attachments











#13

B

bertsmobile1

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


#14

T

tim the pacesetter

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


#15

T

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?

2021-09-23_13-24-36.jpg2021-09-23_13-44-21.jpg2021-09-19_13-14-54.jpg

Attachments





#16

S

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.


#17

T

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?


#18

S

slomo

It's where the fuel goes into the carb.


#19

T

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:

drive.google.com

Toro Carb before.mp4

drive.google.com drive.google.com

After:

drive.google.com

Toro carb after.mp4

drive.google.com drive.google.com


#20

S

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.


#21

B

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


#22

T

tim the pacesetter

slomo said:
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
Click to expand...


#23

S

slomo

tim the pacesetter said:
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:

drive.google.com

Toro Carb before.mp4

drive.google.com drive.google.com

After:

drive.google.com

Toro carb after.mp4

drive.google.com drive.google.com
Click to expand...
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.


#24

T

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.


#25

S

slomo

tim the pacesetter said:
I might end up taking the lawnmower to the shop because things are getting pretty technical.
Click to expand...
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.

1632490873785.png


#26

T

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.


2021-09-19_13-14-534.jpg2021-09-19_13-14-54.jpg


#27

B

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


#28

T

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.


#29

S

slomo

tim the pacesetter said:
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.
Click to expand...
That is your throttle plate. Regulates air flow into the carb.


#30

S

slomo

tim the pacesetter said:
Could this breather tube have been the culprit all along?
Click to expand...
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.


#31

T

tim the pacesetter

Thanks. Throttle plate - got it!

I seem to have 2 welch plugs. When disassembling the carb the first time, one just fell out on its own. I didn't remove the other one because it appeared stuck in there. There's
a little groove/hole on the side that I tried to pry up - but I didn't want to use too much force. Should I just go ahead and really try to pry it out?


#32

S

slomo

tim the pacesetter said:
Thanks. Throttle plate - got it!

I seem to have 2 welch plugs. When disassembling the carb the first time, one just fell out on its own. I didn't remove the other one because it appeared stuck in there. There's
a little groove/hole on the side that I tried to pry up - but I didn't want to use too much force. Should I just go ahead and really try to pry it out?
Click to expand...
Plugs are glued into the carb body. Can be pretty tough to remove. Remove using brute force and a gentle hand simultaneously. The one that fell out needs to be reintalled and sealed. They make Indian Head Shellac which glues and seals these into the carb body. Glue the plug in then seal the round area.

1632603584990.png


#33

S

slomo

Take a bread tie. Strip off the vinyl or plastic covering, leaving a thin wire. Probe all the tiny holes in the carb body and any jets accessible. Spray with carb cleaner and SAFETY GLASSES. I will inform you that if you get that spray in your eyes, it burns like fire. Don't be all cool and try to spray away from your eyes...... That spray KNOWS where your eyes are and will jump in there before you can spit.


#34

T

tim the pacesetter

Thanks for the bread tie tip! That's a great idea. I appreciate the tip on the shellac too.

You are absolutely right about the carb cleaner and how it behaves. The first time I sprayed the carb cleaner on the carb it splattered all over the place - including my face and eyes! It's a miracle none got in my eyes themselves. I mean, I was swiping my eyes with the back of my hand - when that area got hit by the spray too. Next time - goggles or safety glasses. Oh, and I should probably look for the small red spray straw taped to the side of the can next time too. I got lucky - could have been a trip to the ER.

My lawnmower is at a relatives house, and when I went back and snugged up the crankcase breather tube today the engine the surging pretty much went away. The new tube arrived today. I'll install it pretty soon.


#35

T

tim the pacesetter

Hey guys, just wanted to come back and thank everyone for your help. It turns out it was the carb, after all. After I rebuilt it, the mower ran pretty close to perfect. But, I sensed a small amount of surging and figured if I got the float positioned right things would be fine. Well, after I reinstalled the carb after the float correction I could never get it to run right again.

The last step I took was to install a cheap aftermarket carb. No matter what I tried I couldn't get it primed - even after I removed the air filter and poured gasoline through the opening there.

In the end, I had the shop install a brand new Briggs & Stratton (OEM) carb ($41) and they were able to get it running great again. All the shop did was remove the "chinese" carb and install the OEM one - plus they put fresh fuel in the tank.

Just did the lawn yesterday so now I'm back in the game. Thanks again for all your help!


#36

B

bertsmobile1

Thanks for coming back
I am sure when people come here and see all of the techs advocating to use either genuine OEM parts or certified ones from a mower shop they think we are paid stooges for the industry.
However it is just we see all of the dud ones come in for repair.Naturally people who won the parts lottery & got good don't come in so our opinions are a bit biased.
At a guess about 1/10 of what comes through my gate is faulty ebay/amazon parts used to fix a problem that could have been done easily by cleaning &.or adjustments.


#37

T

tim the pacesetter

Thanks, Bert. I was lucky to get an OEM carburetor for my roughly 15 year-old Toro 20038 mower for $41. The chinese/after market carbs were running anywhere from $10 (this carb didn't fit) up to about $30. So, at $41 for an OEM replacement this seems reasonable. I could have used the original carb but since I had my hands on it (meaning I could have damaged it somehow) I figured it would be cheaper to just put a new OEM one in. This way I wouldn't have had to pay a tech to rebuild the original one.


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