Husqvarna lc121p with B&S 725EXi engine low power.

WaltDisney said:
I meant the rocker arms oops, my mistake. And yes I checked the valve clearances at TDC of power stroke and both valves were within sepc.

As for what slowmo asked, the key is OEM and I got the key in accordance with the illustrated parts list, the airfilter is a brand new OEM filter in accordance to the parts list. The carburetor is clean, I took off the sleeve thing of the jet and nozzle assembly and cleaned out the emulsion tubes, the thermostatic choke works correctly. It closes all the way when the engine is cold, and opens up all the way as the thermostat heats up, no binding of parts or any other malfunctions in that system. For the max RPMs I couldn't ever get a good reading as the engine was constantly running poorly with the A.F. assembly on it and I didn't think to check RPMs until it was running fully assembled. And when I was testing out the engine speed, it was over an area of low grass, so nothing was being cut.

I also asked the Husqvarna helpdesk if they had any ideas, the person who answered said that due to the engine speed bogging down when the A.F. assembly plate was installed, it could possibly be the crankcase breather was malfunctioning, which when I inspected the breather assembly, the reed valve was in good shape, it wasn't stuck open on any debris that could have gotten in, nor was it stuck shut from anything either, and the drain hole looked to be open from what I could see, the breather tube itself was clear of obstructions. The Husqvarna rep also said that since there is white smoke coming out of the C.C. breather tube that it could be either: 1. Worn rings, 2. Leaking carburetor, or 3. Too much oil. I know it can't be too much oil as I did an oil change and made sure to measure out how much I put in the engine. Can't be a leaking carburetor as without the A.F. the engine will run fine and if it was a leaking carburetor it would run poorly constantly. So maybe the rings are worn and there's so much blowby that it's agitating the contents of the crankcase and that's what's causing the smoke from the breather tube? However, if it's bad rings, wouldn't my compression tests be reading low? I'm a bit lost there.

Included pictures are of the C.C. breather assembly and the chamber. I had the reed valve removed to inspect the assembly.
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I've gone thru this whole feed and don't see your compression test values anywhere.
 
I didn't see where you replaced the air filter. It could be dirty.. You did say it only bogs down when the air filter is installed.
 
rhkraft said:
I didn't see where you replaced the air filter. It could be dirty.. You did say it only bogs down when the air filter is installed.
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That was one of the first things I did when the old filter was dirty. The bog down starts when the rear plate of the A.F. housing is even placed over the carburetor, it is 100% aligned correctly as it would be if it were fastened into place correctly, and even doing that causes bog down. What makes this even more annoying to diagnose is the fact that once or twice the mower decided to run properly 100% assembled, air filter assembly installed correctly and everything. I honestly can't recall if I did anything different either of those two times. I can't imagine it being a fuel issue at all, the tank is free of obstructions, fuel tank vent is open, fuel line is free of obstructions and restrictions. Carburetor has been throughly cleaned, govner system is working correctly with no binding if parts, autochoke system is working correctly. It's all working fine, besides the low power when even the air filter housing plate is even placed over the intake side of the carb. With that information and the rest of the troubleshooting I've done so far, I'm being lead to suspect worn rings causing excissive blowby into the crank, causing the oil to be agitated too much, which is then exiting the vent tube, and then maybe with the plate even installed loose over the carb intake, without the breather tube installed, it's causing enough of a restriction in the C.C. gasses that it builds up some back pressure? But the C.C. breather reed valve only opens one way - out of the crank, so how could any back pressure be getting back into the crank? But then if it would be excessive blowby, why would the engine be running correctly only if that plate was totally removed from the engine, except for the 2 times it ran normally fully assembled?

See how this is like chasing your own tail in this weird instance? I've been thinking about this a lot today. It's almost like thinking in a circle.
 
WaltDisney said:
I meant the rocker arms oops, my mistake. And yes I checked the valve clearances at TDC of power stroke and both valves were within sepc.
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I'll have to take your word on that one. Every used new to me mower never had valves in spec. But hey yours are. (y)
WaltDisney said:
As for what slowmo asked, the key is OEM and I got the key in accordance with the illustrated parts list, the airfilter is a brand new OEM filter in accordance to the parts list.
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(y)
WaltDisney said:
I know it can't be too much oil as I did an oil change and made sure to measure out how much I put in the engine
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What did the dipstick say?
Measuring is never correct on the money FULL mark. Unless you've changed it before several times and KNOW XX amount of ounces gets YOUR mower ON the FULL MARK?
WaltDisney said:
The carburetor is clean, I took off the sleeve thing of the jet and nozzle assembly and cleaned out the emulsion tubes, the thermostatic choke works correctly. It closes all the way when the engine is cold, and opens up all the way as the thermostat heats up, no binding of parts or any other malfunctions in that system.
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(y) All sounds normal.

I would check, there are two levers that operate the choke. One off the thermostat linkage and one directly controlling the choke plate. They touch each other. These two levers open and close the choke plate. They can get one in front of the other, out of order. My neighbors was this way. Long as the thermostat heats and moves the choke to wide open, should be good.
WaltDisney said:
Husqvarna rep also said that since there is white smoke coming out of the C.C. breather tube that it could be either: 1. Worn rings, 2. Leaking carburetor, or 3. Too much oil.
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If you see a white fog of smoke out the oil sump breather, you have some heavy internal engine damage. And no wonder she doesn't run smooth and proper.

How much oil does it use say mowing for a solid 30-45 minutes?

Do you have to add oil after EVERY mow to bring her back to the full mark?
 
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