From your description, you probably need to adjust both the clutches & the brake.
Most of the time, the clutches are run too tight. The manual gives specific “spool-up” times for a chuck when the clutches are engaged. Follow that time precisely; do not make them tighter as the clutches will heat up really fast / overheat when idling thus causing the dragging you see.
The brake needs to be set correctly as well. If it is too loose, the spindle will keep rotating. Also, the brake needs to release immediately upon clutch engagement.
Some Masters have all mechanical brakes activated by a lever & rod / brake pedal, mine has the electro-mechanical one connected to the clutch lever.
Always set your clutches first. Disconnect the brake during that process. Let the chuck coast to a stop. Only once you have the accel times (in both directions) set correctly, set up the brake.
There is a very fine balance in getting this right. Don’t expect to get it right the first time. Once set though, you can run your lathe practically forever without any hassles. Yesterday I did two 3.5h shifts on it, nothing overheated or started grabbing. It reaches operating temp of about 45* C and stays there. Did some heavy cuts too in 4140: 100 thou DoC, 1030 rpm, 6-8 thou / rev feed.
I would still pull the cover to check the lubrication. Remove the two V-belts from the motor but leave the little pump belt. Now you can start the lathe safely and check how the lube system flows oil onto the clutches. In my machine (and I suspect all the other factory setups as well), the left side of the clutch got lots of oil flow while the right side got very little. So I modified the oil ports (tubes) with little delrin orifices to even out the flow. Now both sides of the clutch (fwd & rev) receive equal amounts of oil. This is very important, imho, especially when the clutches are open (free wheeling) because if one gets more lube than the other, the side with less will heat up, expand & start to drag. The oil carries any heat away.
