77 gs400 to 87 gs450

[Nessism]

Where is the cam chain? You can't turn over the engine with a wad of cam chain a jammed around the crank sprocket. Try holding up the cam chain with your hands and try to turn the engine over then. You should be able to spin the engine over by simply pulling up on the chain. The engine spins CW when viewed from the RH side.

[Brandon77gs400]

I held the chain up before making the video it felt exactly the same. I also tried to pull on the chain. What would happen is it was incredibly hard to pull and then it would give all of the sudden and then I would repeat with the same results. I didn't have this problem before taking it to the shop. I don't understand how this could happen.

[smilinbrad]

I don't like the way this is sounding. I suspect your engine is toast. The bike looks nice though,
I have a 77 400 a 79 425 and an 83 450.. the 400 and 425 look like the same bike to me. Just a slight overbore. The 450 looks like an entirely different animal. I would be surprised if the engines would swap out. I've had no issues with engine internals yet, just lots of grief from carburetors that are gummed up from sitting 12 to 20 years.
Good Luck with your project. They are marvelous little bikes when they run right.

[Brandon77gs400]

I don't like the way this is sounding. I suspect your engine is toast. The bike looks nice though,
I have a 77 400 a 79 425 and an 83 450.. the 400 and 425 look like the same bike to me. Just a slight overbore. The 450 looks like an entirely different animal. I would be surprised if the engines would swap out. I've had no issues with engine internals yet, just lots of grief from carburetors that are gummed up from sitting 12 to 20 years.
Good Luck with your project. They are marvelous little bikes when they run right.

Does it look like the mounts are in the same place? And could the exhaust fit from one to another?

[Spyder]

Pull the stator cover off and try turning the engine again. You said you only had idle issues. If the crank were warped it would vibrate like a washing machine running at 2000 rpm. Could also be a bad bearing. I've had bad wheel bearing in cars that felt just like that. A machine shop should be able to fix almost any problem with the crank.

[Brandon77gs400]

Pull the stator cover off and try turning the engine again. You said you only had idle issues. If the crank were warped it would vibrate like a washing machine running at 2000 rpm. Could also be a bad bearing. I've had bad wheel bearing in cars that felt just like that. A machine shop should be able to fix almost any problem with the crank.

pulled the stator cover off it felt the same. Spoke with the mechanic who looked at it again. He said it should feel and look like that because of counter balancing. So I decided to put the jugs and head back on. Crank feels smooth when there's tension on the chain. I think I'm ok on the crank then. Ordered the service manual; new valve seats, and rings. I'm gonna change those out and then see where we are. Thanks everyone for all the help. It means a lot! I'll get this thing going if it kills me!

[Oldman99]

Glad to hear it feels better. Replacing the gasket under the jugs too? Mine was the stock one and it snapped like a toothpick. I would try to replace all the gaskets from there up so it dose not bite you later on. Good luck!