650 csr tranny trouble

hey all, long time looker first time poster. i have an 81 650 csr that is leaving me a little confused. went for a ride in the nice weather the other day and found i only had third gear. at first i had 1st and 2nd but then something went horribly wrong. no noise or unnatural vibrations, but suddenly i couldn't shift out of 3rd gear. when i depress the shift lever it will just stay down, and will not move up at all. the clutch is working properly or at least seems to. when i pull the lever it will disengage the gears. any ideas of where to start looking, i really don't want to just start tearing it down with out having an idea of what might possibly be wrong. someone has suggested a spring or broken shift lever? any help would be great as it is getting on to spring and the itch to ride gets stronger every day.
thanks
gary
1981 kz650 csr
cincy ohio

I doubt it's the transmission itself, as it sounds like the shift mech is broken somehow. It's pretty simple. It will take removing the left side engine cover and then the small transmission mission cover behind your front drive sprocket. Once these are removed you can see the entire shift mech springs ect, and all can be worked on from that point without further dissassembly.

cool, hopefully i can get to it this weekend. thanks for the quick reply

ok got the cover off this afternoon, and the only problem was a lot of old grease and road grime had gummed up the shift rod where it meets the cover. after some elbow grease and a very thin coating of synthetic oil all is right for now