Sure that discs were not warped?
Barnett CB750 clutch springs are 37mm long.
My K2 has them. Stock clutch model with cheap fibers from Cruzinimage.
My K6 had the golden Barnett springs before with its K6 clutch. (No double metal disc)
Added 2 mm thick washers under them.
Later replaced the clutch, later K7/F2 with double metal disc. No washers. EBC fibers as before.
Had to install the harder black springs for CB500 and smaller bikes to handle the bigger torque

I have had bad working clutch when the adjuster screw for clutch lever inside the chrome cover was released (backed off) too much.
The manual say tighten screw until it stops, release 1/4-1/2 turn and lock with the nut.
When closer to 1/2 turn or slightly more clutch could rattle at idle and take offs.
I did 1/4 turn out. A gentle ride for at least 1/2 hour until engine was warm. Back home and verified that the lever inside chrome cover had play when clutch wire was released.
Double checked again the day after on a cold engine.
I had thoughts about clutch fibers soaked in new oil before assembly could add extra clearance when engine has been warmed up. That affected the adjuster screw setting..
Oil is no longer that thick in clutch package after a ride.
If my K6 start to slip due to wrong adjustment, the fibers and glass beaded metal discs will wear prematurely
Here my Barnett springs, 37mm long.


Almost forgot.
The Hindle 4-2-1 looks good on the bike!

And vice versa!
I like the Hindle sound. When riding gently, gentle sound. Will not wake up the lawmen 's interest.
When using the throttle, pipe will respond with a nice tone.

My K2's Yamiya no number 4-4 are louder when cruising at around 80-100kmh than my K6 970cc with a Hindle.
Niw tou have a good reason for a ride! Your wife too.
I have been worried about what to adjust next giving me a reason for a 200km ride when something finally has been tuned in during and after numerous rides.
So far, new things happens or I start no notice something in need of improvement.
Carbs, charging, handling, new lights/bulbs or just wear the tires to see how long they will last! More I ride faster I will know!!

Next year fuel additives to make the engines shiny clean inside the spark plugs! Redline Si-1 has the stuff doing it. I'll see how .....