Hello, thank you for providing a great site. This is my first post. I purchased a Bobcat 721 with the deutz f2l-411 2 cylinder diesel last December. It was not running, I replaced the fire rings, adjusted the valves and it got it running. It starts right up everytime. But, it smokes, a lot of smoke a lot of blowby and it's getting worse. I tore the top end off and took it to a machine shop, the cylinders are worn down to around 20-25 thousands, and Deutz in Germany does not sell oversized rings anymore (that was my plan, bore the cylinders, new oversized pistons and rings). Now, I'm looking at $1000 for two new cylinder jugs, $250 for standard size rings and $800 for custom made pistons. The reason I am posting is I'm looking for any good advice on repowering the machine with say a f2l 511 or Vanguard or any other engine. Someone with some experience on fitting a different engine up to the hydraulic. I love the little deutz engine, I've used it all summer to load old dead ash trees and spread dirt and gravel. It's just investing so much on an out dated engine makes me think I'm nuts. Thanks for providing this forum, it's great!