fx921 34hp kawasaki back firing no power

[yert42]

i was cutting grass and noticed that i started losing power and after bout 10-15 mins it didnt have enough for power for the pto and was bogging down. so i did some seaching on internet and i thought it was the coil or fuel pump so i replaced both of them and its doing the same thing. its almost like the timing is off but i dont know where to start on checking timing on that and the compression is 125-130 on each cylinder any help would be greatly appreciated thanks

what ive replaced
2 coils
2 spark plugs
clean out carb
fuel pump

 

[yert42]

update on my mower i took the valve covers off and found that the #2 exhaust valve was not opening and closing so im guessing the cam lob is gone or something and this engine only has 272 hr on it!!! has anyone had this problem before? thanks