What is the difference between 2-stoke break-in and 4-stroke break-in for a 2-stoke ABC engine. I need some laymans explanation for this as I have a 2 stoke ABC engine and the manufacturer recommends that never break-in at rich 4-stroke setting. This is Irvine 61 engine.

ABC engines must get to operating temperature as quickly as possible. So the instructions you are reading are telling you this in a round about way. You can tell a 2 stroke is 4 stoking when it is has a low pitch kinda loaded sound (hard to explain but you will see raw fuel sputtering out the muffler). You should always hear that two stroke high pitch wine while breaking in. Remember it should still be run-in with a rich setting as lean settings will burn out your glow plug and can cause damage.

It is really simple to break your engine in. Set the high speed needle to the recommended setting in your manual. This should allow the engine to run in 2 stroke (firing every revolution of the prop) and still allow for a slightly rich run.

Here is how I run in my 2 stroke ABC engines. Start with the manufacturers recommended high speed needle setting. Start the engine at about 1/4 to 1/3 throttle. Quickly get behind your engine and increase to full throttle as soon as possible. Make sure the engine is rich, but it must be in two cycle operation (so that it heats up properly). I run for 30 seconds and then I stop the engine (close throttle). Let cool completly. Do the same starting proceedure and run it for a minute or two (full throttle slightly rich) then stop and cool. I repeat this cycle until the engine holds a good (rich) top end (no sagging - dropping RPMs) at the high end and as soon as it will idle well enought not to give me dead sticks on landing. Then take it off the engine test stand mount in a plane and go fly. Some engines only require a short run-in (usually OS and TT) and some require a bit more (MVVS, Rossi). Your Irvine engine should not take too many runs and it will be great!

Mike

Another good trick is to pre heat the engine with a hot air gun before you start it the first couple times. Also adding a little extra castor to the first few tanks won't hurt.