GVC190 N5BR - BOOM!

Hello everyone.

So, got a free troybilt pressure washer with a Honda GCV190 N5BR engine on there - wouldn't run.

First, had no OHMs...replaced ignition coil - had spark.

Next, discovered it was the exhaust valve completely shut and the piston rings shot causing lack of compression (0, to be exact).

So, long story short, did a refurb on it...got new rings, valves (lapped them properly), made sure to follow the entire service manual on torques and feeler gauge depths, used assembly lube...yadda yadda yadda...tried to do it as best as I could being the novice I am.

Well, she started right up and felt strong. Let her run for about 10 minutes - then shut her down so I could attach the water pump. Got it attached - ran for another five minutes - felt good...then...BOOM.

*Took it apart and you can see the connecting rod completely exploded
*The piston is scored on the exhaust side and the piston skirt blew up.
*The cylinder wall is lightly scored 'til you get to the bottom of the stroke, then it left a nice indentation.
*killed my crankshaft

I need to know why - I don't really care if I spend more than the motor is worth, this is a learning experience for me.

I've looked at the Echo Failure Analysis Report and the only one it kind of reminds me of is the "lean seize." Although, I ensured there were no gaps via utilizing proper gaskets, used RTV properly per Honda Service youtube videos...maybe I had the gas to lean? I don't know.

Any help would be appreciated so I can avoid this error again upon reassembly.

Thanks - Mark