Over the 30 years have been running the M20 I have probably tried every variation you can think of.
The one I found best was welding the drive plates in pairs and running one set short with old worn fiber plates .
Now I do a lot of engine breaking so that might contribute to the extreme corrigations in the drum but the double plates dresses nice & square seemed to last the longest & work best.
Remembering I oxy weld so the welded face tend to be quite soft.
What gets fitted at any particular point of time depends upon what I have in hand or can get either quickly or cheaply ( both better still )
The B series 6 spring could be made to run very sweetly but regularly required adjustments
The next on I hope to fit will be an A10 4 spring if I can get the gear box internals together & working before the clutch is toast
If we ever get the mill happening then I will mill out the battered slots of the drums with sprockets that look a bit less like a WobbyGong shark then braise in some key stock for the tangs to run against .
An old speedway racer did that to my A 10 six spring and that took all of my youthful neglect with flying colours.
I did try to do it myself but my skills with a file leave a bit to be desired and to work the edges of the slots need to be dead square.
I showed this to a club member who worked at one of the universities in the fabrication section and he milled a slot in a couple of lemgths of key steel and braised these into the filed out slots on his A10 outfit and that worked really well for him.
However he got retrenched , the bike went into the mortage & he left the club.
Or perhaps even resprocket some of the toothless ones .