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John Deere 425 blown gasket
| John |
I probably already know the answer to this but just want to make sure. My 425 used to run fine, it always smoked a little but still would mow. Suddenly it will not carry enough rpms to mow effectively. It will engage the deck, but not fast enough to mow. I cleaned the plugs which were pretty bad, did not make a difference. Decided to check the compression. One side was about 190lbs, but the other side showed zero compression. I assume this means I blew the head gasket on that side. I am surprised that the engine runs as well as it does if I have no compression on one side. Any thoughts??
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| John Heine |
Can you hear air coming out somewhere when engine is running? Check and see if piston is moving maybe rod broken.
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| John |
The piston is moving freely, but I still have no compression in that cylinder. There seems to be a little oil coming out from the where the exhaust connects with the cylinder, but I wouldn't think a small exhaust gasket leak would cause a complete loss in compression, would it?
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| John Heine |
I don't think that gasket is the problem better check valves.
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| bontai Joe |
I am thinking that you have more problems than a head gasket as well. If the piston is going up and down, then I'd bet you have a stuck valve, or something else that will require a tear down to fix.
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| John |
If it is a stuck valve, would it be easier just to just replace the valves. I have been reading about lapping valves, and am not sure what this involves.
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| bontai Joe |
No way to tell what's really going on without looking inside the motor
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| John |
OK, so I pulled the valve cover off and noticed that the push rod for the intake valve was not connected to the rocker arm. When I pulled the rod out it was bent at about a 45 degree angle. I pushed down on the exhaust valve and it moved easily, but when i tried to push the intake valve, it was stuck. I tapped it gently and was able to push it down. So I replaced the push rod and ran it again. No difference, so I took the valve cover off and had bent the intake push rod once again. This time I pulled the head off and both valves had a good amount of carbon on it. I assume the push rod is bending because it is not able to push the valve open. Is there anything else that would cause this?
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