First you get a bobber and a fishing hook...<G>

Just kidding.

All you newbies - never buy a .40 anything. Save yourself money and grief later on and buy as big an engine as you can that will fit in the forty sized trainer that you are considering. Plain bearings, ball bearings, it doesn't matter, but there is no replacement for displacement. Buy at least a .45 for your trainer.

One fellow pretty much wrapped up my opinion of the OS .40 LA in this one statement, "The OS .40 LA is the best .25 I've ever owned".

All kidding aside, these are good solid engines, but they can be difficult to put to further use after flying your trainer for a while. What puzzles me is why the engine companies bother making a .40, a .46 and some go on to make a .50, .52, .53 and a .58 in essentially the same size crankcases. It would make more sense to start out making these engines as large as you can and then forgetting the smaller iterations. By making just the one size, they could sell the large engine for the same price as the smallest one they would normally make. The end user would have a better, more usable engine for a larger variety of airplanes, etc. But of course, we know that "they" don't want you to reuse your old engine, but instead want you to "move up" in size and sophistication.

When it comes to .40 size engines that share a similar mounting dimension format to larger engines, follow Nancy Reagan's lead and "Just say no".