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No throttle response

#1

V

viperv10

I have a Lawn Boy duraforce gold model 10525 that I put a new carb on. I hadn't used it in a long time and I noticed the tank was empty. There was black oil all over the deck that was coming out of the muffler.
Very little oil was under the carburetor. I checked the carb and the float, needle and seat seemed to be just fine. I then turned the mower on its side and took the blade off to get to the plate that holds the exhaust u pipe on.
Probably about a half cup of gas and oil came out. The u pipe was about half full also. I couldn't figure out how all of that gas leaked through the engine and down into the exhaust. When I put the old carb back on I noticed gas was leaking from the side of the carb through the pilot jet opening. I tightened it up real tight but it still seeped out. So then I installed a new carburetor. When it starts up on full throttle it runs about 3200 rpm, but when I pull the throttle lever back it doesn't slow down a a bit.
I got down and looked and the throttle linkage seems to be working ok. When it is on choke the linkage is all the way to one side. As you pull the lever back the linkage slides all the way over the the other side. I checked my other dura forces
and they seem to work the same way. Does anyone have an idea about why there is no change in rpm when moving the throttle cable? Also does anyone have any ideas about how the gas tank could empty out and come out the exhaust
when the engine is not running?
Tank you.
Jerry


#2

FuzzyDriver

FuzzyDriver

Haven't worked on one of the newer models, but if it has the F-engine Walbro then I'd suspect governor adjustment or a stuck air vane. Can you easily move the vane fully back and forth with your finger? The throttle control doesn't directly control the vane position, it controls the tension on the spring. To reduce RPM the vane has to overcome the spring tension. If either the vane physically can't move or the spring is too tight (so the vane can't overcome it), the throttle will stay open. Forgive me for mentioning this, but if the throttle disc is missing from the vanes shaft then that would also keep the engine running at high RPM.


#3

I

intruder1500

Check out this You Tube video....may be what you need.



#4

I

intruder1500

And on the gas tank....carb float sticks and gas runs thru the carb to the point of least resistance. Had the same problem on both my 10525's and here's a fix ....



#5

V

viperv10

I checked the spring on the air vane and it came loose from the throttle cable linkage. Just the opposite end of the spring that came loose in the video.
I also have an add on shutoff valve. on this mower but very rarely use it, but I will now.
Thank you for your reply. I don't know how that spring could have come off. I just recently installed the new carb. I have had these and F engine carbs on and off many times.
Regards,
Jerry


#6

FuzzyDriver

FuzzyDriver

Glad I could help, Jerry. I've got three F-engine carburetors on my workbench right now, two plastics and one Walbro. Did you check that the right spring is on it? Some are shorter and if your carburetor is looking for a long one...
Are you saying you have two fuel shut off valves on it? Did the factory one quit stopping flow?


#7

V

viperv10

No, Dura force engines don't come with shut off valves like the F engines do. It should be the right spring because it came with the new carb.
I asked the question about if there was a difference between the throttle spring on a F engine and the dura force on this forum awhile back but I don't think anyone answered.
They look the same but have different part numbers. I ordered two new springs for dura force and when I got them they looked identical to the F engine throttle springsI have.
The air vanes work the same on both engines.
Regards
Jerry


#8

R

Rivets

If your crankcase has raw gas/oil in it the cause is most probably a bad float needle and seat, allowing the fuel to flow easily from the tank through the carb. They may look good, but still do not work properly. Time to replace.


#9

FuzzyDriver

FuzzyDriver

Yeah, Rivets. Jerry pretty clearly had two separate problems. There's no way the spring being off filled the crankcase, but what you said about the cause of that issue makes perfect sense, especially if the gas tank isn't shut off.


#10

W

wineman

viperv10 said:
I have a Lawn Boy duraforce gold model 10525 that I put a new carb on. I hadn't used it in a long time and I noticed the tank was empty. There was black oil all over the deck that was coming out of the muffler.
Very little oil was under the carburetor. I checked the carb and the float, needle and seat seemed to be just fine. I then turned the mower on its side and took the blade off to get to the plate that holds the exhaust u pipe on.
Probably about a half cup of gas and oil came out. The u pipe was about half full also. I couldn't figure out how all of that gas leaked through the engine and down into the exhaust. When I put the old carb back on I noticed gas was leaking from the side of the carb through the pilot jet opening. I tightened it up real tight but it still seeped out. So then I installed a new carburetor. When it starts up on full throttle it runs about 3200 rpm, but when I pull the throttle lever back it doesn't slow down a a bit.
I got down and looked and the throttle linkage seems to be working ok. When it is on choke the linkage is all the way to one side. As you pull the lever back the linkage slides all the way over the the other side. I checked my other dura forces
and they seem to work the same way. Does anyone have an idea about why there is no change in rpm when moving the throttle cable? Also does anyone have any ideas about how the gas tank could empty out and come out the exhaust
when the engine is not running?
Tank you.
Jerry
Click to expand...
Stuck air valve or you are missing a sealing gasket. What is the condition of the Dowel pin?

Tom in Dallas


#11

V

viperv10

Hello
I'm not sure what air valve you are talking about. It does have all 3 gaskets that go on a dura force carb. My problem might be that it is a cheap Chinese carb. Ebay is loaded with them.
Used to be that you could only get the oem ones that came unassembled. You have to put each piece together. That is a good learning experience. But any way I took it back off and everything inside is
is clean as a whistle. I turned the carb upside down and blew into the inlet tube. I could hear a tiny bit of air flow so I bent the float stem slightly so it would seal better. Tried it again and got dizzy from blowing so hard but heard no air coming through the needle and seat. Put it back together and it wouldn't start, not even with starting fluid. It does have good spark. My wife was watching the spark plug against
the fins while I was pulling the starter rope. I quit for the day and turned the gas shut off valve off. The next day I smelled gas in the garage and there was black oil under the muffler and underneath
the mower. I took the carb off again and replaced the new needle and seat with new lawn boy brand parts and it still leaks and still wont start. I did notice the Chinese carb had a 1pc. main jet instead
of the 2 pc. main jet and nozzle that comes on the original ones. Also there is no screen filter and it uses a cheap rubber bowl gasket.
I am going to take the carburetor off another dura force that runs good and swap it out and see if I can get it to run. If that doesn't work then I'm about out of ideas.
Regards
Jerry


#12

FuzzyDriver

FuzzyDriver

I don't know which is worse, unreliable junk new parts or the unavailablity of the air filter base and air filter cover on walbro carburetors. I'm going nutty trying to finish up the rebuild on this Walbro!

Are you sure your test was valid? I'm thinking that there''s a difference between the Δyour breath/weight of float and Δfuel pressure head/float buoyancy. I'd leave that known good carburetor on overnight, too, after you see if it runs.

Good luck - and, I don't guess you have any Walbro air filter parts laying around? :)


#13

V

viperv10

Do you know what the model no. is of the mower or the part no.s of the air box and cover? Steel deck or alloy ? I have seen black air boxes and green covers on Ebay lately.
I have 4 or 5 F mowers around but I don't think I have any extra air filter covers, but I will look.
Regards,
Jerry


#14

FuzzyDriver

FuzzyDriver

I'm not sure that the exact part number matters on Lawn-Boy Walbro carburetors. I know that a few years ago I got a black one that had two rows of air inlets on the outside instead of the openings at the bottom that the green ones have and it worked fine. The exact match for this Walbro would be 612504 for the base and 611377 for the cover. All the models that start with S21 (~1989) are the same. I almost hate to mention this, but while you're looking, if you have a plastic carburetor air filter cover in very good shape I'd give you $25 for it. These have a turtle and a rabbit molded into the cover.and are part number 611376 (~1984).

I see you are in OH, I'm just across the border north of Toledo.


#15

V

viperv10

Sorry, I couldn't find any filter boxes, but on ebay there is an air box #612504 black for $14.99.
I couldn't find a 611377 but if google part # 931231 several places have them. That's the one you were talking about that is black and has the 2 slots in the front.
I have a cover like that on a V engine lawn boy that came from Lowes. That stuff for the F engines is getting harder to find. Walbro's are getting harder to find also.
I found a NOS walbro 2 or 3 years that will fit on a lot of F engines, but they want a lot of money for them.
I'm about to go swap carbs now and see what happens.
Jerry


#16

V

viperv10

I ordered a new toro carburetor yesterday morning on Amazon that came from Jack's small engines in Md. and it got here today. Now that's fast.
So I assembled all the parts and installed it on this problem child. I also checked the compression and it was 90 psi. I'm not sure were it should be.
But any how, the mower started on the first pull. It smoked a little but ran pretty good. I only let it run for about a minute because it was 11:00 at night
and I didn't want to upset the neighbors. Will check it out again tomorrow. The Toro or Lawn boy carbs have a main jet that screws into the nozzle.
The chinese one was one piece without the main jet. That might be part of the reason it wouldn't run. I don't know. I wouldn't recommend them to anyone.
I have used a lot aftermarket coils with good results though.
Regards
Jerry
PS
Oh the sweet smell of success, and 2 stroke exhaust.


#17

FuzzyDriver

FuzzyDriver

I have been searching for one for days, including 93-1231. All the hits I found ended in "Out of stock", "Unavailable", etc. Did you find one that was available?

V engine as in V-twin??

I don't need a Walbro carburetor, at least right now. I need to finish the three carburetors I'm working on first.

F engine compression when cold is 100-115, with a minimum of 80. Not sure if 90 is OK for the duraforce, but it is certainly good enough for the engine to run. I also have not had an issue with aftermarket coils. For that matter, I've found that a few minutes with my heat gun restores some original coils to work. This never makes sense to me, hot does cooking an electronic device make it start working again??

2-stroke exhaust...gotta love it. I use Klotz - smells even better, and the mosquitoes hate it.

-Mike


#18

V

viperv10

The V engines I think might stand for value. They were sold in the nineties at box stores. They had black shrouds, black handles and steel decks, with plastic carbs. I believe the air filters and boxes
were the same size as on F engines. The ones I have seen were 4.75 hp and 2 stroke.
I googled lawn boy part 93-1231 and found several hits. https://www.russopower.com/parts/toro-93-1231
partmartusa.com

OMC Lawnboy Air Filter Cover 93-1231

OMC Lawnboy Air Filter Cover 93-1231 Replaces Toro 145831, Toro 609641, Toro 610177, Toro 610384, Toro 610728, Toro 610742, Toro 611376, Toro 611377, Toro 93-4303
partmartusa.com partmartusa.com
https://powermowersales.com/Toro-93-1231.
Copy and paste each of these web pages and see if this helps.
Also look up lawn boy part 8481AE on Ebay, There is a used air box, cover and bolts for sale.
You are right the part # 612504 is out of stock or discontinued. Yesterday there was one on Ebay.
Regards,
Jerry


#19

I

intruder1500

FuzzyDriver said:
I have been searching for one for days, including 93-1231. All the hits I found ended in "Out of stock", "Unavailable", etc. Did you find one that was available?

V engine as in V-twin??

I don't need a Walbro carburetor, at least right now. I need to finish the three carburetors I'm working on first.

F engine compression when cold is 100-115, with a minimum of 80. Not sure if 90 is OK for the duraforce, but it is certainly good enough for the engine to run. I also have not had an issue with aftermarket coils. For that matter, I've found that a few minutes with my heat gun restores some original coils to work. This never makes sense to me, hot does cooking an electronic device make it start working again??

2-stroke exhaust...gotta love it. I use Klotz - smells even better, and the mosquitoes hate it.

-Mike
Click to expand...
Possibly moisture in the coil itself and heating it up solves the problem.


#20

FuzzyDriver

FuzzyDriver

Jerry, I was trying to avoid that one on eBay because it's in Canada, but I went ahead and bought it today. Never bought any parts from up North before, crossing my fingers.

As many hours I've spent searching for that air cover you'd have thought I'd found Russo before. Thanks so much. I ordered 4 of them.

As many times as I've checked eBay, I don't see how I could have missed that 8481AE base. Maybe it just was put on in the last couple days - I know I've searched eBay for "Lawn-Boy Cover" lots of times. Anyway, thanks again!

-Mike


#21

V

viperv10

Right On


#22

FuzzyDriver

FuzzyDriver

Jerry, just FYI, my order for 93-1231 with Russo failed. They also didn't have other parts that show up on their site as both "Discontinued" and "Available in stores": 612504 (air filter base) & 611376 (Turtle-Rabbit air filter cover). Yeah, that was a head scratcher alright.

Oh, and the 8481AE on eBay? The seller also had a box of Lawn-Boy parts for sale for $19.99. Not too attractive until you get to the last of a bunch of photos - the last photo was of three Walbro carburetors! I went from ho-hum to [Buy It Now]!


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