Hi, first plane, first engine, first post here.
I am a raw newbie, but bought a plane from a m8 which has an Irvine 40 engine.
Despite knowing nothing, I stripped down the engine,(great idea for a newbie ) and cleaned it up with carburettor spray.
I think I know how to put it back , but am not 100% sure about "which way around" the piston goes.

The piston has a little rectangle cut out in it , so could anyone describe which way around in the sleeve it goes.

Also as the engine is bone dry now, do I need to oil it before trying to start it etc, will I need a torque spanner to put the head back on etc.
Any advice appreciated, cos I know nothing ( didn't stop me taking it apart though).

Pajo,

The rectangular hole in the piston is to prevent masking of the boost port, when the piston goes down.

It goes on the piston side, opposite the exhaust.

The Schneurle ports are angled on both sides of the exhaust ports and the third "boost" port, usually with slightly shorter open timing, is angled up, opposite the exhaust post.

The ports are all angled, so as not to spew the fresh mixture out of the open exhaust port.

Don't get the carburettor spray on plastic and neoprene parts.

Use after-run oil, or ATF (or Marvel air-tool oil) for assembly.

Thanks a lot for your help m8,
some of your reply was a little over my head at the moment but hopefully after reading a lot here, I will learn a bit .

just to clarify
is the following correct.

the piston is inserted in the sleeve with the rectangular hole in the actual piston, facing directly opposite the large rectangular hole in the sleeve which is the exhaust port, which also means the hole in the piston lines up with the "squarish" hole in the sleeve.

Thanks again, and sorry to be a pain.

Pajo,

I don't have a photo of the Irvine sleeve, but from the top down, the one port which is highest is the exhaust port. It faces the exhaust stack in the cylinder casing

On either side of it are slightly lower, angled ports, "fed" by the Shneurle bypasses in the cylinder casing.

Very slightly lower is a third port, fed by the third "boost port", opposite the exhaust in the cylinder casing. The hole in the piston must face this port, which apparently has another "squarish" hole in the sleeve for bypass clearance.

Fresh boost mixture passes through the piston hole -> through the "squarish" sleeve hole -> up the boost bypass -> into the cylinder, through the boost port.

Thanks m8.
Off I go rebuilding.