Bench testing starter, how fast do they spin?

[eric67]

Have a 97 Challenger and i'm bench testing the starter. My mechanical skills are with cars and a few motorcycles. I know if i bench test a car starter it spins like crazy. I took the starter apart, cleaned it, and sanded some slight rust off the armature where the brushes contact. I bench my 787 starter with a battery charger 2,10, and 55amp. It seems like an even speed, not very much torque. This is a SBT high torque 1-2 years old that came with the rebuilt motor. Is that what these starters are suppose to spin?

I charge my battery and get 2-3, 5-10 second cranks out of this starter before it won't spin the engine anymore. Battery load tests good. Spark plugs out, the motor spins fine.

thanks for all the help...