https://www.hitchcocksmotorcycles.com/partsbook-pages/2369Hitchcock's online parts book shows the KS assembly guts are much like the 4 speed unit.
The KS shaft is stepped and rides in the inner cover as well as the outer cover as "bushings", actually the inner & outer case/cover. There is also a spring and an inner transmission shaft needle bearing (vs bushing in the 4 speed).
If the transmission is shifting properly, the needle bearing is likely OK. The KS shaft can be too tight in either (or both) the inner cover or outer cover. Maybe the covers are misaligned. Maybe there's some corrosion or gasket sealer on the shaft. Possibly there is some voodoo going on with the KS return spring.
In any event, at least have a look under the outer cover. Carefully try the KS without the outer cover to check for binding there.
If the KS shaft is binding in the inner cover bush, that will need to come off too.
BEFORE removing the inner cover - have a new gasket & KS pawls in hand. Have a manual in hand.
Be aware the gear shafts can "stick" in the cover instead of sliding politely off. This can pull the gear guts out of position, leading to much cursing. Usually a soft-face mallet carefully applied can keep the shafts politely sliding back thru the cover as it's being removed. I'd ask other 5-speed doctors here for the secret dope before pulling the inner cover for the first time myself. The 5-speed box is definitely busier than my 4-speed units.
IF you pull the inner cover, closely examine the KS shaft for evidence of cracking. One of mine "spiral cracked". I'd just replace the pawl whilst in there for good measure.
These machines can develop multiple unrelated failures, comes with the turf. Good hunting! - ACR -