Jim, if the piston or head gets too much carbon build up, everytime TDC comes around it can stress the rod and could lead to failure.
Decarbonizing the combustion chamer is on the list of recommeded periodic maintainance. Have a peek inside there and see how things look. This could be one of the many things that could have caused this to happen.
The above post by Brian is precisely the reason we do not hesitate to recommend him. He could have easily said something like " you get what you pay for" or he could have just said nothing. Instead, he comes forth and comments favorably on the feedback, and admits he cannot touch the price. Thanks Brian!!
OEM parts...Ford/Gm/etc are usually always more $$$, otherwise NAPA/Auto Zone etc would not be in business. Any yes there are aftermarket parts for Kohler/Onan/Briggs that are very good....and some that are not so good. Sticking with those that are recommended here by fellow members is your best bet.
I hope you guys realize that the parts sold by reputable companies like Stens and so forth are exactly the same parts you get from Kohler, Kohler more than likely get their engine parts from an outside source through a tender system. These same suppliers supply parts to Stens and many others for instance, Kohler charge much more because of the Kohler name on the packaging. Where problems arise is when you get parts from "offshore" suppliers in China or wherever they are made and sold here by someone that is in it for a fast buck. These tend to have brand names like "OEM" or something like that. Addmitedly it is a game, but don't be afraid to buy aftermarket as long as it is good quality stuff. I was once told by a guy he only used "Briggs & Stratton" oil in his engines, well B&S don't have a refinery last I checked so guess where they get B&S oil? They tender out and as long as the oil meets their minimum requirements they buy what is cheapest, key word here is MINIMUM, which is not very high so that opens the market to China,Japan and a million other countries. These companies only want cheap for the biggest markup possible and the people supplying are not going to give the best they have for rock bottom prices submitted in the tender just what meets requirments.