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This mower lost a exhaust valve into the cylinder due to the retainer wearing out. Got it put back together and it starts and runs ok, but it looses power after it mows awhile and will not start till it cools down. I was wondering if the flywheel key might be partly sheared. Just asking before I start diassembly.

doublee said:

This mower lost a exhaust valve into the cylinder due to the retainer wearing out. Got it put back together and it starts and runs ok, but it looses power after it mows awhile and will not start till it cools down. I was wondering if the flywheel key might be partly sheared. Just asking before I start diassembly.

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Has to be heat related. Coil, tight valve ?? A sheared key wouldn't be heat related at all.

reynoldston said:

Has to be heat related. Coil, tight valve ?? A sheared key wouldn't be heat related at all.

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I was thinking that the timing may be retarded some do to a partly sheared flywheel key would that make the engine run hot.

doublee said:

I was thinking that the timing may be retarded some do to a partly sheared flywheel key would that make the engine run hot.

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Could be but not likely, not that big of a job to check or replace that key.

Dropping the valve into the cylinder can crack the piston or head.
When the engine gets hot the crack opens up and you loose compression.
When it starts playing up turn off the engine and pull the dipstick.
If you get smoke signals from the tube then you are leaking into the crankcase.
Cracked piston/ cracked ring / gouge in the side of the bore.

There was a reason why the valve dropped in the first place
Did you find that and address it beore reassembly ?

If not the original problem might still be there causing overheating