Agree fully with the other posts, it's a great little engine in either 40 or 46 size. Runs forever and makes great power on 10%. Sure, it's no 46AX but then it's not trying to be the top of the line sports engine but rather a very honest workhorse that will last forever.

I can't help but comment how fellow club members are always asking me if I've done something to my 40LA, it copes with all but the worst of winds and revs nicely at 12000RPM. They can't believe how good it goes.

Pull the baffle in the muffler, change to 10%nitro (I don't see the point in more), and tune it for peak revs. You will know when you've gone too far as it quickly runs rough, turn it back a few clicks from peak power so as to ensure a safety margin.

If it's dead-sticking all the time either the idle is too low, the engine hasn't fully run in, or you have it way too lean. Better to run it too rich to start with until it's had quite a lot of fuel through it (say a gallon), after that you can lean it right out for power.