'77 GS550B gearbox noise help

Chuck78

Been Around the Block
On my wife's 77 gs550b, her original engine was getting a little low on compression, and the gearbox would get stuck in neutral from time to time and not shift into gear when traffic lights would turn green... We got a 78 gs550 engine with like-new compression, and swapped it in. Shortly after, this bike started getting stuck in first gear, and would not go into neutral or second.

A little while after that, it started making an intermittent loud knocking noise at idle or low speeds (engine and road speeds both). I am pretty certain this was coming from the gearbox as well. The bike was way up on power after the swap (pods/straight thru Dunstall glasspacks/rejetted), and was run through the gears very aggressively on many occasions. In my very limited knowledge of these gearboxes, my only instinct was thay maybe a shift fork was bent and sticking somewhere in there.

Anyone have any diagnostic speculations or tips or insight on this??? It's otherwise a very solid engine.

The original with the occasional stuck-in-neutral problem is on the bench for an eventual teardown and total rebuild with GS650 cylinders/pistons/head to make it a gsxr carb'd 9.6:1 673cc mill, so I'm trying to figure out what's wrong with both gearboxes.

Thanks for the guidance.
 
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