If one is familiar with them, then pulling it off would be a half-way decent indicator. If you aren't too familiar with them, then the only red flag would be a horrible, way too obvious build-up. You can take off the right hand cover and rev it up to see if the arm moves around 6,000 RPM or so.
On a different subject, I think you had mentioned something about changing the shock spring. I am thinking that you did, anyway. If you did, I think you would be OK for the stock rate. Just measure the sag to be sure.