Intoduction.

Hi all, I am Erhard and I am new here with old mowers and lots of problems. My friend and I have both a Nova Canadiana mower These mowers are perhaps fifteen years old and are equipped with a Briggs & Stratton Power built 12 hp power engine. Both of them are popping badly and I found that on mine the cylinder walls are very worn and by now is not even starting anymore. When I saw the condition of the cylinder I thought I may want to re-bore it and get over-sized rings and piston. That seems, however, not to be possible as the cylinder walls are chrome or nickel plated and if re-bored the piston would run in aluminum. Therefore, it seems they are plain and simple through away units. Which is remonissant of the GM's Vega. That too was a smashing success and soon discontinued. I now would like to find a suitable substitute engine. Any advise?