Just a WAG here, but it sounds like the valve is sticking open.
That allows enough "slop" in the valve train to "release" the push rod.

You might try mixing an upper cylinder lubricant in the gas, such as Marvel Mystery Oil or similar and see if that reduces/stops the problem.
Maybe a fre oz. in the oil too.
Kind of a band aid approach, but simple.

I would think the underlying problem may be a bent or gummed up valve stem????
Does it get regular oil changes with a GOOD quality oil?

Hi,

Thanks so much for your thoughts. I've read them to my husband who thinks you have an excellent idea and he will try your suggestions. I'll let you know what happens. He takes very good care of his equipment and I know he uses good oil, changing it often.

Thank you again and Merry Christmas!

As an after thought-
He might want to remove the valve cover and manually move the valve back & forth. Maybe spray the stem with carb cleaner/WD 40 or something similar to see if it dissolves any gum/varnish etc. before the "manual manipulation"?

I meant to say a FEW oz. in the oil in my initial post.

DO get back and let us know if it helps!
It's so frustrating when people never respond back to see if we were helpful. Feedback can often help someone else with a similar problem-

Bill has given great advice as usual. When you do pull the rocker cover and check the valve movement, verify that the guide itself hasn't slid out of position and is holding the valve from opening completely. I don't know the probability of this happening on the Kawasaki. But it is starting to happen on Briggs twins. At least more often than it should.

Thank you both for the kind help. I will most definitely let you know how everything works out. What a great way to help people solve problems!

I have a john deere eztrack z225 zero turn mower it runs great until you engauge the pto then it shuts down any ideas?