Honda HRR2162SDA Self Propelled Moves Slow

HRR2162SDA
MZCG-6943463

This has a one-speed transmission. When I engage the clutch cable, the wheels turn but the mower moves very slow. It will go up a hill, but, again, slowly.

I've worked on this model before and the problem was the clutch cable had "stretched". Replacing the cable fixed the problem.

However, I recently spent hours working on an HRR216K5VKA with a similar problem. I replaced the clutch cable and repaired the Smart Drive only to find out that the problem was the control arm on the transmission was hitting the transmission case because the transmission was worn out. The only solution was to replace the transmission. Here's the thread HRR216K5VKA

Are there any adjustments to the clutch cable on this model? I have not seen any. That is an adjustment nut on the back of the mower under the Discharge Guard. I turned this clockwise numerous turns, but it had no effect.

I checked the control arm on the transmission that is attached to the clutch cable. The control arm is not hitting any part of the transmission. With a screwdriver, I could push the control arm towards the transmission about 1". So it would appear that a new clutch cable would engage the control arm more. But there may be other problems I am missing

Questions:
1. Is there a way to adjust the clutch cable?
2. What are the troubleshooting steps to determine why the mower moves slowly when the clutch is engaged?
3. What does tightening the nut under the Discharge Guard (which is attached to a spring near the pulley) supposed to do?

Thanks.