If the engine was pulled out and all you have is the engine, it could simply be that they pulled the hose off the head and it spilled into the intake. The hose is right above the intake. Typical procedure for removing the engine is:
1. Remove Airbox and muffler
2. Remove Carbs.
3. Disconnect hoses.
So with the carbs gone and the hose right above the intake, it is really common for people to just pull the hose off and spill all the coolant from the top down onto the intake. I always put a rag down to cover the intakes when removing the hoses.
What is the plans for this motor? You might just get a new gasket set ($50) and pull the head off and replace all the O-rings. If you know the compression is 130-130 or better, then I wouldn't pull the cylinders off. I'd probably get some cheap 2 stroke oil and just fill the crank crank case up and let it sit for a day. Shake it up and then drain it.
Depending on your plans for the motor though, that would dictate what I would do if it were me. For example, if you're going to put this in an Ultralight, then rebuild the whole thing. If you're putting it in a snowmobile, then just do the gasket set.
2015 Skidoo Renegade BC 600 Etec
1999 Skidoo Summit X 670 HO (Son's)
1996 Skidoo Touring E 380F (sister's)
1995 Skidoo Summit 583 LQ
1985 Skidoo Tundra 250F
1999 Arctic Cat Jag 340F
1999 Arctic Cat Z 370F (son's) - needs track
1990 Arctic Cat Jag 340F
1982 Arctic Cat Panther 440F