My 2 cents, doubtful it was sabotaged, if it was froze up from it being sabotaged, there would be some sort of tell tale sighn, weather the cylinder being badly scored from something being put in it, or rusted all to hell from water being in it, which in theory could come from a leaky head gasket. When you unfroze it, there went the rings, and compression. If it was indeed sabotaged, you would know with out a doubt.
That being said, if it sat a long time, its very possible mosture collected and rusted up the cylinger walls, or head gasket could have been leeking and didn't know it with or without oil being poured in it, sitting water still would have caused problems. It may very well have been tired in the first place with lower compression, it also could have hot seized after it was rode hard and parked, there is a lot that can be in play.
Electrical, there is another thing,spark could have been fine when parked, a loss of spark just happens. They are old machines, and coils wear out. You can ride 1 day with great spark, get on it the next, and its cooked, nature of the beast.
Check all your connections, check for good ground, test your plug coil, take the boot off, cut it back a little and re attach the boot if the coil tests good. If that all fails, see if your ohm readings on the stator are in spec, if not you have a bad stator. Check the pins on cdi for corrosion, and the female plug that plug into the cdi, my problem was a pain to find, and it was one of the female pins that plug to the cdi was loose.
If thats it winds up it I have a few stators I can sell you one. If stator is in spec check flywheel key to make sure it didn't shear, and if none of that is the case, pull the fly wheel, shake it around and if it rattles, the magnets are broken. And you need a new flywheel.
If you need any parts, I have a good oe plug coil, oe stator, and oe flywheel, and oe cdi.
Good luck.
