No throttle response

viperv10

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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
 

FuzzyDriver

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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.
 

viperv10

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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
 

FuzzyDriver

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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?
 

viperv10

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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
 

Rivets

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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.
 

FuzzyDriver

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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.
 

wineman

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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
Stuck air valve or you are missing a sealing gasket. What is the condition of the Dowel pin?

Tom in Dallas
 
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