Hi Can somebody tell me the measurement to adjust the center nut on a single spring clutch on a 1931 B31-2 . Is it trial and error , or is there a set amount the spring is compressed. Thanks
The nut needs to be done up tight. Unfortunately there is no adjustment.
There was an army mod done to the nut to help adjustment on the M20. Try the WDM20 site for the info.
I find it's trial and error. I screw the nut up until about 1 thread of the hub is showing, refit the dome and pushrod and try to kickstart the bike. If it slips, I screw it in another complete turn. I find that if it doesn't slip on the kickstart, it doesn't slip on the road. If a lot of effort is required to pull the lever in, and the clutch still slips, you may need to boil the friction discs in detergent, especially the one behind the chainwheel, which gets covered in oil with use. Maybe fit new friction discs. Hope this helps.