# Toro 4 cycle lawnmower surges while running



## BC99

I just bought this Toro (used). It starts quickly, but once running it surges and will not go to full power. I have changed the filter...working on the plug now. Any other thoughts. 

Otherwise in pretty good shape...just unused for quite a while.

New to this forum...first post, but like to tinker.


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## 30yearTech

Model and serial number of your Toro or Brand and model number of the engine please.


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## geogrubb

First, welcome to the forum;
As 30year stated we need the engine info, without it you are asking, "How long is a rope".
If it is surging, normally have a fuel restriction, which would indicate a dirty/varnished carb sometimes this can be remedied by cleaning different areas of the carb, however without knowing what you have, we have no idea what to tell you. Have a good one. Geo


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## BC99

30yearTech said:


> Model and serial number of your Toro or Brand and model number of the engine please.


Model number 26622, SN 9010709. Replaced the plug with no improvement.


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## BC99

Thank you and I understand. It is a Model number 26622, SN 9010709. I expect that it has been little used, but has sat for a very long time without runing.


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## 30yearTech

BC99 said:


> Thank you and I understand. It is a Model number 26622, SN 9010709. I expect that it has been little used, but has sat for a very long time without runing.


As geo suggested, make sure your carburetor is clean. Particular attention should be paid to the Pilot Jet ref # 11 in the illustration below. If this is restricted in anyway, it will cause the engine to surge constantly.


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## BC99

Thanks....will try this and let you know how it turns out. What a great resource this forum is!


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## 30yearTech

You can try cleaning out the pilot jet first, as you can access it from the top of the carburetor with out taking the carburetor apart. It has a very tiny hole in the bottom and 2 larger holes on the side, be sure they are clear and then give it a try, if it still surges, then the carburetor may need to be torn down to clean. You can look at illustrated parts pictures like the one I posted at Toro's website. If you can't find them let me know and I will get you a link.

:thumbsup::thumbsup:


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## BC99

Thank you again for past suggestions. I have since cleaned the pilot jet and changed the fuel filter. Through it is better it still surges. However, I notice that the throttle arm leading to the carb moves back an forth while the engine surges seeming to indicate that the choke is being closed and opened. When I stop the throttle arm from moving the engine runs up to high speed and seems fine. Does this indicate some other problem?


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## 30yearTech

That is the throttle that the arm operates and not the choke. The governor may be out of adjustment and causing the surging. Perform the static governor adjustment and see if that takes care of your surging.

Locate the governor shaft where it comes out of the engine block. Loosen the arm that is attached to the shaft. Hold the throttle on the carburetor to the wide open position and note which direction the arm attached to the governor shaft moves. While holding the throttle wide open rotate the governor shaft in the same direction it would turn to open the throttle, turn it until it stops. Tighten the arm back down to the governor shaft. Thats the procedure for making the static adjustment on any internal governor, horizontal or vertical.


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## Bob DiGiacomo

Just a thought. Watch that the fuel line is not hitting the throttle linkage. I was working on a Toro and that was the problem that I had after I put the carb back on. Good luck.


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## BC99

Thanks again guys. Good thought on the fuel line but not the problem. I did follow the guidelines for adjusting the governor resulting in no surging but with no throttle control from full on down to engine shut off. No speed control in between. When I returned the governor to the original position the engine went back to surging at full throttle, with low engine speed and the governor arm rocking back and forth as the engine surges. 

Other thoughts? 

EDITED FOR CLARITY FROM THE LAST POST.


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## 30yearTech

If it's still surging with a properly adjusted governor. Then the problem lies either in the carburetor or there may be an air leak between the carburetor and cylinder. You can check for an air leak by spraying some carburetor cleaner around the mounting points between the carburetor and intake manifold while the engine is running. If you get any change in the way the engine runs when you spray the cleaner, then this may be an air leak.


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## Pac51

Hi All,
Great site. I am here because I have a Toro 2662 purchased new in 1989. Has run beautifully and GTS until this year. Took 4 pulls!! Can't beat that.
Anyway, it is surging and I found this page. I have registered, etc, but can't seem to get the PDF file of the Carb to open. It tells me I am not authorized to view it. Any help? Thanks.


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## 30yearTech

Pac51 said:


> Hi All,
> Great site. I am here because I have a Toro 2662 purchased new in 1989. Has run beautifully and GTS until this year. Took 4 pulls!! Can't beat that.
> Anyway, it is surging and I found this page. I have registered, etc, but can't seem to get the PDF file of the Carb to open. It tells me I am not authorized to view it. Any help? Thanks.


You can look at a illustrated parts list for your mower at the Toro website, but you will need to recheck your model number as your missing at least one digit. Most likely cause of the surging in the engine is a dirty or restricted pilot jet in your carburetor.

https://lookup3.toro.com/partdex/index.cfm?xCaller=Toro


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## wayne_etc

Sorry to pull this thread up from oblivion, but I found it while searching for a solution to the same problem, same kind of mower.
I found that really cleaning out the pilot jet had the biggest impact on reducing the surge. Before, my mower would surge with the blades engaged and also without the blades engaged. It was so bad that any type of load would cause the motor to bog down and stall. After cleaning, the motor still surges without the blades engaged, but is smooooth with the blades engaged. I just finished mowing my 3/4 acre lot and all is well.
Anyone know why it still surges without the blades engaged, but is smooth WITH the blades engaged?

w


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## 30yearTech

wayne_etc said:


> Sorry to pull this thread up from oblivion, but I found it while searching for a solution to the same problem, same kind of mower.
> I found that really cleaning out the pilot jet had the biggest impact on reducing the surge. Before, my mower would surge with the blades engaged and also without the blades engaged. It was so bad that any type of load would cause the motor to bog down and stall. After cleaning, the motor still surges without the blades engaged, but is smooooth with the blades engaged. I just finished mowing my 3/4 acre lot and all is well.
> Anyone know why it still surges without the blades engaged, but is smooth WITH the blades engaged?
> 
> w


The surge under load was likely a restriction in the main jet. No load surge is likely some partial restriction in the pilot jet, or the low speed circuit of the carburetor. A worn throttle shaft could also affect smooth operation.


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## frostykev

Wayne, Did you end up fixing this? I'm about to start working on mine, I know its winter almost, but I really don't want to buy a new one when this does what it needs to. Mine surges before load, but engage the blades and the engine revs stronger, not as strong as I think it could. . . but with a bit of TLC I'm hoping I have a near new 22 year old mower next spring. I'm going to start with the pilot, then rebuild the carb if needed. 

30YearTech, how would I test for worn throttle shaft or low speed side of the carb?


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## 30yearTech

frostykev said:


> 30YearTech, how would I test for worn throttle shaft or low speed side of the carb?


You will need to physically inspect the throttle shaft to see if it's loose in the carburetor body. If the low speed circuit of the carburetor is plugged, then you can hold the throttle with your finger at a low idle speed and the engine will usually stumble and most likely die. This is a good indication the the idle circuit has an issue. A good cleaning may be all that is needed.


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## junebug1701

frostykev said:


> Wayne, Did you end up fixing this? I'm about to start working on mine, I know its winter almost, but I really don't want to buy a new one when this does what it needs to. Mine surges before load, but engage the blades and the engine revs stronger, not as strong as I think it could. . . but with a bit of TLC I'm hoping I have a near new 22 year old mower next spring. I'm going to start with the pilot, then rebuild the carb if needed.


I have the Toro 26624, basically the same mower but with electric start. The Mikuni carburetor can be very finicky. Mine sat for years and the varnish took it's toll. After what I thought was a thorough cleaning, it still wouldn't run. As 30year said, make sure that pilot jet is clean, but also in my case the main nozzle needed attention also. I took both those parts (numbers 11 and 21 in the diagram above) and ran them through an ultrasonic cleaner. That did the trick, and now it runs as it should.


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## frostykev

30 Year, when you mention a good cleaning, are you referring to the outside or open it up, new gaskets and clean all the individual parts? 

Can you clean the pilot jet without opening the entire carb?

I'm surprised at the gasket/rebuild kits are so much, any cheaper places for gasket kits?

Junebug, Glad to see another old toro running!


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## 30yearTech

frostykev said:


> 30 Year, when you mention a good cleaning, are you referring to the outside or open it up, new gaskets and clean all the individual parts?
> 
> Can you clean the pilot jet without opening the entire carb?


Unfortunately cleaning the outside of the carburetor only makes it look good, but does nothing to help the engine run any better. The pilot jet can be removed without taking the carburetor apart. Many times the carburetor can be taken apart and cleaned out without needing any new parts, if your careful taken it apart.


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## cegtv

*carb adjustments*

hello i have a toro model 26622 serial # 90242226

what are the initial carb adjustments for each screw and can i buy any wheels for the back, or do i have to get them from toro mine are bald and slip during use thanks paul


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## 30yearTech

The adjustment on your carb is only for the low speed set it to one turn from seat. The rear tires are specific to your model, so they will need to be for your mower but there maybe aftermarket ones available.


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## light mechanic

I had a lawnmower shop in SW Louisiana back in the early 80's and I sold several lines and on of them was Toro, they had the best machines on the market, once you sold one of the walk behinds unless it was a Carb. problem they did not come back and have several that I have sold are still in use, had to have clean fuel, when you clean the carb. take your time and clean, clean, clean, I think I still have the shop manuals for all of them I will look this weekend, scan them and put them on here, Light Mechanic


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## brucep

30yearTech said:


> You can try cleaning out the pilot jet first, as you can access it from the top of the carburetor with out taking the carburetor apart. It has a very tiny hole in the bottom and 2 larger holes on the side, be sure they are clear and then give it a try, if it still surges, then the carburetor may need to be torn down to clean. You can look at illustrated parts pictures like the one I posted at Toro's website. If you can't find them let me know and I will get you a link.
> 
> ??


Hello and thank you! I just joined the site to say that I have been fighting the surging problem with my old Toro 2 stroke lawn mower. I love this old mower and hated to give up on her. I am an aircraft mechanic by trade and supposed to know what I'm doing but I was stumped. I had cleaned the carb, checked the float level, the springs, set the choke, _thought _ I had cleaned the main jet (#11 you suggest starting with.) Nothing changed. Still surged, and died under load. Then I got on your site here and read that that jet has a tiny hole at the botttom tip. I pulled that jet again, and used one very tiny strand of wire. The tiny hole was clogged for sure and it took me a little while to open it up. I put it back together a while ago and it has never run so perfectly! 
Thanks again,
brucep


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