Yashica Mat LM - Testing Shutter Speeds

Can anybody tell me if there is any way to operate the Yashica Mat LM shutter with the back open?
I just got a shutter speed tester and have been checking my large format shutters but can't figure out if there is any way to check my Yashica.

Thanks for any help you can give me
Dave

Hmmm....wind the camera forward and back to the rest position? Yes, you don't have a hard stop going forward, but going backwards should have a stop.

Thanks Dan - I just got the camera and still learning about it. I didn't realize I needed the top spool in place as well but it looks like we're good to go now.

Dave