My bike suffers from balky/clunky shifting as well. Shifting from First to Second "was" resulting in mis-shifts into neutral unless I gave the lever a good hard pull into second. Even up/down shifting to 3rd-4th-5th was always clunky.
2 days ago I decided to thoroughly flush the area around the shifter where it comes out of the engine case with silicon spray lube and then repeatedly sprayed small doses of "Blaster PB50" Teflon Lube directly on the shaft/seal while rocking the shifter back and forth.
Yesterday I went for a 5 hour ride and all the shifting problems were gone!!! except a bit of balkiness shifting down to 4th.
I have been using this product on a lot of things for some time now, including the kickstand, trailer door hinges, car door hinges, garage door rollers etc, etc. ...with AMAZING long lasting results.
BTW... I also pulled the top cover off the throttle cable housing at the same time and sprayed multiple doses of PB50 down into the cables as well as directly onto the carb throttle plate shafts...twisting the grip has never been that light.
Available here for 'great white north residents'...not sure where US riders would find it.
https://www.canadiantire.ca/en/pdp/blaster-pb-50-multipurpose-lubricant-with-teflon-0380403p.html
