Topic: Cb650 stuck engine /busted crank?

[78whiteorbs]

Picked up a 1980 cb650 for 90$ complete and was told the engine was stuck.
Got it home and started investigating and shifted into 5th and it would roll. Would roll every gear with some resistance so I thought great , its not stuck!!

Tried starting it and no dice, jumped the clicking solenoid and could hear the starter tryng to engage but would not turn over the engine. Stuck a screw driver in the plug hole and pushed it in gear and the pistons weren't moving up and down . removed the points cover to learn the 650's in 80 had an electronic iggy,neat.
rotated the crank bolt and it felt as though it was moving the pistons a revolution at first and then nothing ,just free spinning round and round and round... The PO said they poured some mystery oil in it trying to unstick the engine and never could get it . I am thinking they might have wailed on it busted the crank , is that possible?
Gonna tear the engine down to see what happened. Just wondering what could have went wrong. Opinions welcomed.

[Dimitri13]

 I am intrigued.

[78whiteorbs]

well, the transmission is shifting and turning but the pistons aren't moving. Weird, every bike with a stuck engine I have encountered would NOT move an inch in gear.

[dave500]

youd never bust a crank by hand,youd bend the bar your leaning on or shear whatever is attached to it first?

[trueblue]

Possible the clutch is knackered, either that or the primary chain is busted.  I would say that when you heaved on the end of the crank, you sheared the little pin behind the advancer.  It was never intended to take that sort of abuse.  Honda even said to remove the spark plugs before using it to roll the engine over.  I would be extremely surprised if the crank is busted.

[78whiteorbs]

Clutch actually works, when it is in gear I can pull the lever and it pushes easily, let out and its as you would expect.
Thinking now ,that makes since that the pin make be sheared. I had no idea it was not literally the end of the crank . I believe it did roll over some ( I did remove two plugs but couldn't get to the center two) then must have sheared. SupposeI can remove the clutch cover and have a peak, looks like should be able to see in there pretty good from that angle.

[trueblue]

Take the alternator cover off.  There is a big bolt in there you can crank on, without much fear of breaking anything .