SV610-3213 Fuel Delivery Problem?

Has to be something going on inside this engine. Replaced coil due to wire damage and no change. OK I'm desperate so I will try a new spark plug.
 
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Seems the ignition switch has been opened before and the internals were put together incorrectly causing a short to the blue wire in all positions except off. Fixed this and I had significant improvement to the longevity with blades engaged, but fuel starvation is still problem. I can mow at about 40% throttle for a while, but anything more it starts to bog down, cutout and sputter. Disengage blades and I can get it to continue running. Maybe I will remove the anti-backfire valve since I have a fuel line shut-off valve.
 
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The Push mower said:
Seems the ignition switch has been opened before and the internals were put together incorrectly causing a short to the blue wire in all positions except off. Fixed this and I had significant improvement to the longevity with blades engaged, but fuel starvation is still problem. I can mow at about 40% throttle for a while, but anything more it starts to bog down, cutout and sputter. Disengage blades and I can get it to continue running. Maybe I will remove the anti-backfire valve since I have a fuel line shut-off valve.
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The anti-afterfire valve aka Fuel solenoid has nothing to do with fuel going into the carb. It's soul purpose it to help prevent that loud bang after shutting off the key. It will not prevent fuel from entering the carb, and will not prevent the carb from overflowing when the key is off if the float valve has failed.. The float valve controls the amount of fuel entering and controlling the amount of fuel in the fuel bowl.

Make sure there is nothing partially blocking the fuel inlet in the carb. Sometimes garbage will get caught up in the area between the fuel line inlet and the float valve seat which will act to cause fuel flow restriction. Or something partially blocking the fuel outlet on the fuel tank.
 
ILENGINE said:
The anti-afterfire valve aka Fuel solenoid has nothing to do with fuel going into the carb. It's soul purpose it to help prevent that loud bang after shutting off the key. It will not prevent fuel from entering the carb, and will not prevent the carb from overflowing when the key is off if the float valve has failed.. The float valve controls the amount of fuel entering and controlling the amount of fuel in the fuel bowl.
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If you are running along and the anti-backfire valve loses power the mower continues running? My understanding is the valve closes as soon as engine is turned off blocking off fuel so it does not end up in the exhaust causing the "backfire" as the engine winds down those last few strokes. One problem I am thinking is something to do with an intermittent signal to the valve due to the keyswitch problem mentioned in previous post.

Put the original carb back on and filled tank to 1/2 and get an even better result- higher RPMs (not full) and almost no cutting out UNLESS I am going forward up a hill then it gets really bad and cuts out and if I can turn around fast enough and point the nose down the hill it will stop cutting out. I have verified fuel flow at least four times. All new rubber, filter and shut-off valve. Tank, elbow and grommet were both removed. Blew air thorough at 30psi-perfect flow. New fuel lines have very little sag below carb inlet.
 
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Intermittent cutout of the fuel solenoid would create more of a engine sputtering and backfire situation as it opens and closes, not something that you would keep running with using the choke or even preventing with kicking out the PTO.

Went through a similar situation last summer with a customers mower. Finally find what was causing the issue after having the carb apart on 4 separate occasions. Finally dug a small ball of cottonwood fluff out of the fuel inlet on the carb this was after carb cleaning and 90 psi air through the fuel inlet from the float seat outward.
 
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The solenoid plugs off the main jet
On some carbs they will continue running on the idle jet
So it does not affect fuel coming into the carb, it stops fuel going through the main jet
If for instance if the float needle is not cutting the fuel off then the bowl will over fill & fuel will enter the engine via the float vent hole
This of course looks like very rich running and can take anything up to 1/2 to come into effect depending upon how much fuel the engine is using and how bad the float needle is leaking .
That one took months to nail down but after that pressure testing float needles became SOP ( you don't fool me twice easily ) .

Now because there are governed engines, the throttle control you move does not directly control the throttle butterfly in the carb
All it actually does is set the upper limit of butterfly opening
So when sitting there the butterfly could be open say 10%
When you start to move & put a load on the engine it will open another 5%
But when you turn the blades on and put a big load on the engine, the butterfly will open as far as it is allowed to .

If you have a fuel blockage or air leak then the engine should surge and that surging can be reduced a little by closing down the choke a little
As your engine just cuts out I am tending towards thinking you have too much fuel
Running fine on low throttle settings where the fuel is being supplied mostly via the idle jet then spluttering & dieing when the throttle is fully open and the main jet supplies the bulk of the fuel is exactly what happens when the main jet is way too big ,loose or missing all together .
The latter is very common with the Nikki carbs that have the plastic plate as it gets blown out during cleaning and if you don't know it should be there, you don't miss it .
On the twin barrel carbs the main jets are held in with just the O rings so regularly fall out but in this case you see them when you pull the carb apart .
 
The Push mower said:
Put the original carb back on and filled tank to 1/2 and get an even better result- higher RPMs (not full) and almost no cutting out UNLESS I am going forward up a hill then it gets really bad and cuts out and if I can turn around fast enough and point the nose down the hill it will stop cutting out. I have verified fuel flow at least four times. All new rubber, filter and shut-off valve. Tank, elbow and grommet were both removed. Blew air thorough at 30psi-perfect flow. New fuel lines have very little sag below carb inlet.
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I believe this is a gravity system. You say you replaced the filter. What filter are you using? Paper element? You are describing a fuel flow problem with the uphill downhill difference. Try removing the filter and running it and see what happens.
 
Here is the final problem. The nipple from a fuel filter broke off inside the last section of fuel line connecting to the carburetor-wasn't me. I had blew air through the lines and observed fuel flow out of the line, so I thought flow was OK. Today I decided to remove and LOOK through every section of hose and found this piece, which was just enough to reduce fuel flow causing fuel starvation. WOT w/blades engaged while mowing up a hill again....

 
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