I have my Dyna on the lift. Doing a pipe change and doing some PM. I want to change my transmission and primary fluids. Normally I ride the bike and drain the fluids when warm. Will it be ok to do a fluid change cold? Should I flush with ATF?

 

It's nice to do it right after a ride when warm because "stuff" is in suspension in the oil & doesn't have time to fall out of suspension & settle. However, if it were me, already up on the lift, I'd go ahead & change it. No reason to flush trans w/ATF unless you see moisture (as from condensation) in the oil, on the dipstick, etc. As for the primary, I run ATF in there regularly. Clutch likes it (bike clutch is just like an auto trans clutch pack) & that stuff has so much detergent in it, it will keep things clean in there & wash friction disc wear debris out of the clutch. Besides that, it's cheap compared to other oils.

 

Is it really necessary to disconnect the neg. battery cable when changing the primary oil?

 

No it is not.

 

You could just remove the drain plugs and leave it overnight. The only problem is that the chaincase drains best on the jiffy, the trans when the bike is upright!