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Briggs Stratton engine model 4P90HU 420CC exhaust valve retainer wore out and let valve go into the cylinder. The valve is bent, cylinder is ok. Is any one else having this type of trouble with the valve retainers. Engine only has 24.7 hr's on it.

First off this isn't a Briggs engine, it is the MTD manufactured engine. this is the first one that I have heard of with valve retainers issues, and there are no service bulletins available relating to this problem.

How long have you owned this mower.

ILENGINE said:

First off this isn't a Briggs engine, it is the MTD manufactured engine. this is the first one that I have heard of with valve retainers issues, and there are no service bulletins available relating to this problem.

How long have you owned this mower.

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It is a Craftsman 2 years old. It had a rod to go through the block with 1 month to go on the warrenty . sears put a new complete engine on it and it run 24 hr's before it quit. checked it a little closer and found that the cap on the end of the valve was hitting the retainer instead of the end of the valve stem, checked the intake valve and it is hitting the valve stem end like it should. i also checked the hardness of the retainer with a file and it was real soft metal. One stroke with a file cut a groove in the retainer.

The softness sounds like (more) quality problems. Cut back in one area (like receiving inspection) and pay in another. Metal that would not harden or no hardening took place? For fun heat the retainer with a torch cherry red and quench in a little can of used engine oil and then give it the file test again.