G'day

Not quite sure what you mean. A photo or two would help but I think what you are proposing should be OK.

I strongly suggest you put the engine into a test stand to run it in. You will find it quite a bit easier to get to know the engine on a test stand than mounted in a plane - especially if you plan to mount it inverted. The ASP engines like some running before they fly. They can take quite a bit of running-in before they will idle well and they usually need the low speed needle to be tuned quite a bit as they usually come out of the factory set pretty rich. As much as an hour of running in may be needed. They are not "out of the box" runners like OS.

I would also suggest a fuel which has some (about %5) castor oil in it. The ASPs seem to like this and they don't like a lot of nitro. 5 to 10% usually works well with them. Once run in, you can reduce or remove the castor but I always use some as insurance against rust and lean runs.

Four strokes have the lock nut because they can back-fire and throw the prop especially if they are lean. Slight too little prime and they can throw the prop at you and with a 120 size engine, this is going to be a 14 inch prop which can do quite a bit of damage.

You will need a good electric starter to start this engine and a fresh battery. Alternatively you can do the "back flip" start if you know how to do it. (Prime the engine, wind the engine back against compression, then wind it forward about 180 degrees, apply the glow starter then flip it backwards against the compression with a chicken stick. It should bounce against the compression, fire in the forward direction and then start.

If you had bought a 56 size engine, I would say just give it a go, but with the 120, I would ask someone who knows these size engines to give you a hand initially. They can be quite dangerous if you don't know what you are doing. They have a lot of power and they aren't afraid to use it.

All the best

Mike in Dubbo, NSW