G'day

As a previous poster said "If it ain't broke don't fix it." Every time you pull an engine apart you shorten its life quite a lot. For your other engines, I would pull the back plate off and have a look and perhaps put some general purpose oil in there - something like 3 in 1 and then see if the engine feels free. If it does, run it. The "rust" is often just oil residue and will be cleaned out with a good run.

When faced with a stuck carby, I just warm them with a heat gun or gentle flame and they then loosen up. Once they do, then oil them as above. It is a good idea to blow fuel through the carby from both directions (ie blow some back from the needle engine) to push out any dried fuel residue.

If you do pull the engine apart, make sure you mark the conrod so you know which way it goes back and the piston too. And look out for the nick in the top of the LA liner which has to line up with a pin. Not sure about the AX but it probably had one too.

Have fun

Mike in Oz