Should the bike be level and upright when checking brake fluid level in the master cylinders? Owners manual doesn't say. I think yes but not sure on this one. 2010 EGC

 

You want the master cylinder to be level to prevent any spillage thats all that maters.

So for the rear brake Yes have the bike level.

For the front brake move your handlebars to whatever position gets it as level as possible.

And dont get any on your paint!

Good luck.

 

Front……..on jiffy stand, turn handlebars left.

Rear….MC vertical, if possible.

…….at least on my bike.

 

and what is the fill lever on the rear MC? I am a touch low but the manual does not say how far to fill it....

 

A touch low as you say is probably ok. Personally, I would only fill it full if I had brand new brake pads. As the pads wear the fluid level will go down. If you fill the master cylinder with used/worn brake pads then it will be overfull and quite possibly overflow when you depress the caliper pistons for new pads.