[J. Baker]

Does it die with PTO on or off

That's a really good question to ask!
Two different paths for the OPS system depending on if it is on or off. Also, if it does it with it both on and off, that will eliminate a lot of possibilities.

 

[cboudet]

Does it die with PTO on or off

It runs fine until you load the engine with the pto or moving forward.

 

[sidemouse.ii]

If there is one thing I am sure of is that the problem is not the choke. It works perfect, nothing cracked on the linkages. If it was choke related the engine would begin to run rough, but the engine runs smooth, warms up and dies under load.
Thanks.

Cool.
You might still want to read through that FH721v thread, it covers quite a few possible causes to do with the "cuts off / loses power once warmed up," the one thing I regret ... Which didn't end up being the problem anyway, but when I was adjusting the valves I should've pulled the pushrods and checked them for straightness because there's a documented issue in that direction as well.

 

[Justin Hightower]

It runs fine until you load the engine with the pto or moving forward.

Lemme narrow it down a little more. You say it dies when moving forward, does it die when you first move it forward, or when you disengage the brake? Sounding like it could be a faulty seat switch seeing how it immediately starts back up (your putting the brake back on to start it).

 

[cboudet]

I wish it was something as easy as that, but that is exactly how it feels.
No,the seat switch has been bypassed.
I can start the mower when it is cold and the engine runs perfectly smooth. It will move and climb an incline without feeling it, then after a minute or so,when it warms up, you try to move forward, backwards or engage the blades and it dies. I think it is something internal with the engine that when it warms up it looses all the power. I wander if a warped head will do that.
I did not get the parts I ordered yesterday, so I will have to wait until the weekend to work on it again because I work until 7.
Thanks

 

[cboudet]

And none of that would cause it to die suddenly as if the key was turned off.

I Read the old thread,
Thanks

 

[cboudet]

Parts arrived.
I will do some more checking befor I start replacing.
Can someone comment on this question that I have, at the end of the paragraph:
"I can start the mower when it is cold and the engine runs perfectly smooth. It will move and climb an incline without feeling it, then after a minute or so,when it warms up, you try to move forward, backwards or engage the blades and it dies. I think it is something internal with the engine that when it warms up it looses all the power. I wander if a warped head will do that."
Thanks

 

[sjessen]

Any possibility that when the engine over revved that it blew the new head gasket? Only thought about a warped head is that the engine might still run on one cylinder so missing vs shutting off completely.

 

[J. Baker]

I think it is something internal with the engine that when it warms up it looses all the power. I wander if a warped head will do that."

No.
Well, it could I suppose, but highly likely. And not within a minutes time, and not without being very noisy. Usually if a head is warped that bad and leaking you can hear it.

I think you’re chasing your tail.

 

[cboudet]

Any possibility that when the engine over revved that it blew the new head gasket? Only thought about a warped head is that the engine might still run on one cylinder so missing vs shutting off completely.

Yes, I haven't over-reved it but don't think that the symptoms are those of a blown head gasket, and it doesn't run rough.
Thanks

 

[cboudet]

No.
Well, it could I suppose, but highly likely. And not within a minutes time, and not without being very noisy. Usually if a head is warped that bad and leaking you can hear it.

I think you’re chasing your tail.

Yeap.

 

[J. Baker]

Yeap.

“Yeap”?
Are you agreeing that it isn’t a head?
Or that you’re chasing your tail?

 

[cboudet]

My tail.

 

[Breezmeister]

My tail.

Yea, been there done that when it comes to electrical problems...I have been burned with what I thought was a good battery. At a minimum, I would do a draw down test.......Free at most auto parts store if you don't have the tool.
.

 

[J. Baker]

Yea, been there done that when it comes to electrical problems...I have been burned with what I thought was a good battery. At a minimum, I would do a draw down test.......Free at most auto parts store if you don't have the tool.
.

I’ve had that happen once on a Chevy Blazer 20 years ago. Battery dead shorted inside suddenly. Had 12.? Volts on it but wouldn’t start the car. Changed the starter and cables. Didn’t fix it. Put the charger on it just to bring it to full charge and the battery got HOT. That’s when I found it. Glad it didn’t blow up when I charged it.

 

[mrskydrol]

Just a thought. It sounds like the fuel mixture is leaning out when the engine warms up and stalls when its loaded. If you can choke it and it will start again I suspect a leak in the intake manifold between the engine side of the carburator and the engine when the engine warms up. Check for warpage or gasket that is thin, etc.
Also, I am assuing the carburator you replaced was new, not rebuilt?

 

[sidemouse.ii]

So you had an engine that kept blowing crankshaft seals and to replace it you bought a used engine from someone who stated it "ran great but keeps blowing head gaskets..." I am not sure I would label an engine that keeps blowing head gaskets as a "great runner" but let me leave that for another discussion.

Common issues with the FH721 and related series engines is overheating due to clogged or plugged cooling systems, the problems associated with overheating (such as warped heads) and loose valve guides which can result in bent pushrods, blown head gaskets and so on.

Granted, this wouldn't cause it to die like it was shut off ...
If you want to go further into the overheating discussion I can do so, but it relates more to a mower that struggles under load... It will die if you push it and engaging a PTO will certainly do that, but if you disengage immediately it should recover even if sluggishly which would lead me to further search in the areas of overheating due to crud buildup and loose valve guides and warped heads and such... But again even with a warped head it would still run warmed up, it just won't run good.

So perhaps the issue is electrical, perhaps a wire is shorting out against the frame someplace but then wouldn't it do the same when cold? Might be worth looking underneath at the clutch connector... If that comes loose or if it has 3 wires and (I think) the ground wire is disconnected then it will kill the mower when engaging the clutch but also when moving the stick(s) because of the logic circuitry, still odd that it won't do it when it's cold...

Which leads me back to the ignition coils.
You stated you replaced these, if I recall correctly.

 

[cboudet]

Just a thought. It sounds like the fuel mixture is leaning out when the engine warms up and stalls when its loaded. If you can choke it and it will start again I suspect a leak in the intake manifold between the engine side of the carburator and the engine when the engine warms up. Check for warpage or gasket that is thin, etc.
Also, I am assuing the carburator you replaced was new, not rebuilt?

I changed the carburetor, I robbed the old engine which ran great, it is not new.
Thanks

 

[hal]

Did you clean it first?

 

[J. Baker]

I changed the carburetor, I robbed the old engine which ran great, it is not new.
Thanks

Did you use a new gasket?

If you start the engine and let it just sit and run at half throttle but don’t drive it, will it die just sitting there running?

Edit: I see now you said earlier it doesn’t die until loaded, but I’m still curious to know if it will run at mid to full throttle not under load indefinitely?

Also, simply engaging the PTO kills it?

We may need a video to help you further.