I have an OS 40LA (from my trainer) which was in a crash from a radio glitch some time ago, it seems to have no damage, actually the crash was no big deal, broken apc prop, bent landing gear, crack in fuse.

After the crash i removed it from the airplane (got it repaired and donated it to the club for the new students who don't have an airplane yet and wanna "taste" the hobby before putting money into it), got it cleaned, oiled and stored

Today i was looking for some stuff and ran into the engine still in its bag, took it out to re-oil it and spin the crankshaft a couple of times

I felt a "bump", like compression but not as "soft" as compression bump, removed the carb and backplate and spin it, the bump is still there, it can't be compression cause it has no plug, carb or backplate

What do you think it is?