Am I looking at a complete cleaning of the unit? It starts slow and accelerates with time. This happens in DC and DCC. Had the unit as new from Atlas bought a number of years ago. Has run for at least 30 hours.
Most likely the unit has old congealed lubricant that gradually warms up with running. Most likely source is the motor bearings or the drive shaft bearings although it would not hurt to clean and re-lube everything.
All engines need a few minutes of warm up time before it gets to operating speed. Even those that are cleaned and properly lubed. That's why when you speed match, you want to warm them up first by running them before adjusting CVs. How much of a speed difference is there and how long does it that to get there?
Gentlemen, thanks for the feedback. After running 6 minutes I noticed a 20% increase in speed. At this point the engine was constant. I think I will eventually open her up and give a cleaning.