few tips.

after finishing a run ALWAYS run the engine out of fuel.

nitro attracts moisture . moisture in the engine is a "BAD THING"(tm)

use afterrun if you plan on storing it for a while. (few weeks? use best judgement) also "mavel mystery airtool oil" works well and some people have had good results with automatic transmission fluid too.

since you are not sure of your engines condition when you do get to it.. take the pipe and header off and rotate the crank till you see the top of the piston. rust will most likely start at the edge of the piston so you can see it... if its not rusted... run it and defuel it properly.. if it is rusted its not a judgement call for you. you can take it apart and and resurface the piston with ultra fine steel wool (not sure of the grade but there is steel wool that is REALLY fine) of the rust isnt too bad... or replace the piston and sleave if its bad...

note the bearings could aslo be rusted... so when turnign the engine feel for any grinding.