You don't need to do anything to an LA.40, just use the correct size venturi, prop, plug and fuel. You will find lots and lots of stuff written on the LA.46, but people shy away from the .40 for some reason. I have run several of them, and like the FP.40, you can run them stock, you just have to use the core t set up initially. Start with a venturi in the .250, range if you are using an OS needle valve, get a variety of 11- 4 and 11-5 props, some GlowDevil Long plugs, and some good 5% and 10% nitro fuel with at least 20% total oil and have a tachometer in your flight box. The tach will be for just making sure you launch at the same RPM each flight. Then have some fun!! There is plenty written up in this section on these engines, so get some practice with the search function and read up on things.  Welcome back!!
   Type at you later,
   Dan McEntee

I have a couple of new OS 40 LA motors that I can use ,but I need to know what needs to be done to make them a RELIABLE stunt engine for plane in the 40-43 OZ. range. I don't plan on competing, I just want to fly for fun. Looking forward to turning circles again. Thanks, Greg Steffen

  *Do NOTHING to the engine*, it is already reliable enough, do not modify and it and don't let other people talk you into modifying it.  Don't even take it apart, just put the stock muffler and stock venturi on it, use something like an 11-4 or 11-5 prop, and go fly.

   This engine has astronomically more power than a Fox 35, is much more reliable, and can safely run in a 2-stroke. We replace Fox 35s with 20FPs and 25LAs for tremendous performance improvement, and this is 60% more displacement. The biggest problem will be slowing it down, hence the lower-pitched props.

    Brett

Greg, do what Brett said, don't touch your LA40. Put it in a1 plane and go fly it.

I had an LA40 in a Vector 40ARF, 47oz RTF. Flew very well.

Craig