Hi all,

'85 K100RS

I have just completed my first clutch spline lube successfully ( without removing exhaust system).

During initial strip down I noticed a 7mm o/d hard plastic tube going down thro' the rear of the gearbox casting into the region of the swinging arm. This was not connected to anything at the top end.
I can only guess that this has been a vent for an older style "wet" battery.
Can anyone confirm or offer an alternative suggestion.

thanks again folks

Ian

Could it be a vent tube for the gas tank ?

Yes, if it's going through a hole in the left rear top of the transmission then it's an old obsolete battery vent/drain hose.

+1 on battery drain hose.  Not necessary when using a maintenance-free AGM battery.