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

Is it possible that you are crushing the crankcase vent tube that attaches to the back of the air cleaner assembly? That backing is also what bolts the carburetor and the metal bracket assembly.

Did you watch the video I sent you?
 
Are you 100 per cent sure you have the timing correct? I pull back or kick back is a big time indicator that the timing is off or is still off.

Did you torque the flywheel down? I have had several Briggs engines where I installed a new flywheel key and failed to torque it properly. The key sheered quickly
 
Auto Doc's said:
Is it possible that you are crushing the crankcase vent tube that attaches to the back of the air cleaner assembly? That backing is also what bolts the carburetor and the metal bracket assembly.

Did you watch the video I sent you?
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I watched the video yes, I did everything he mentioned. The C.C. breather tube isn't crushed and fits snugly on the back of the A.F. plate where it slides on.
andrewslarge said:
Are you 100 per cent sure you have the timing correct? I pull back or kick back is a big time indicator that the timing is off or is still off.

Did you torque the flywheel down? I have had several Briggs engines where I installed a new flywheel key and failed to torque it properly. The key sheered quickly
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I've torqued it down and even gave it some extra with my impact drill.
 

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I hate to mention this, but these engines do have a plastic cam gear that can skip a tooth and throw the valve timing off. That is showing to be one of the weak areas of this engine design. The lobes can also shift on the metal core of the camshaft.
 
Auto Doc's said:
I hate to mention this, but these engines do have a plastic cam gear that can skip a tooth and throw the valve timing off. That is showing to be one of the weak areas of this engine design. The lobes can also shift on the metal core of the camshaft.
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Right, I've heard of that being an issue and I was hoping it wouldn't require something like that.
 
I believe Auto Doc has given you the next steps in trouble shooting this engine. He’s usually spot on. Unfortunately this will take a bit of work and a new gasket or two. You can do it!
 
The cam issues wouldn't cause a problem when you put the air filter plate on. That's gotta be blocking air/fuel, or binding a linkage or something like that, IMO.
 
Mark H_NO said:
binding a linkage
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The only linkages are for the govner and throttle, and the thermostatic autochoke, both of which I cleaned and lubricated around to be double sure.
andrewslarge said:
I believe Auto Doc has given you the next steps in trouble shooting this engine. He’s usually spot on. Unfortunately this will take a bit of work and a new gasket or two. You can do it!
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That might end up as the last resort.

I have tried using another A.F. back plate that has more of an opening on it. This one fits on the carburetor and still accepts the old air filter. The plate with the janky drill holes are from the old one, the old one even has that weird restrictor around the bottom opening which would defenitly lower the amount of air getting in. While I was messing with the A.F. assembly I noticed that when I had the C.C. breather tube attatched to the A.F. plate, then and only then would RPMs drop, whereas if the C.C. breater tube vents to the atmosphere and doesn't even go into the A.F. housing, the RPMs are normal. I can't imagine this would be the actual solution to all this?
 

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The backing on the left is for auto choke models, not sure about the one on the right. Maybe it's for a primer bulb type system?
 
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