2020 YZ 250 clutch springs

Heavier springs are going to reduce slipping. If slipping is your problem and your cable is in fact adjusted correctly then you need to change your oil to an oil designed for motorcycles.

You shouldnt be going through a clutch every 20 hours on a brand new yz. IF your cable is adjusted correctly, and IF your oil is indeed yamalube, and IF your clutch is assembled correctly and your bolts are to the correct torque(this gives your spring preload), your clutch will work perfectly fine. Triple check it all before putting random springs in it from other bikes.

I'm assuming yz250 2 stroke. Which yamalube are you using? They make all different viscosities/applications, you just want to make sure it is one best suited for your transmission. Maxima MTL is a proven one for two stroke bottom ends if you want to try something else in attempt to isolate the issue, but the correct yamalube is not your problem. Really soak those fibers as long as you can before install, smearing it on with your finger moments beforehand won't do it. Do everything kb228 says, uniform torque of the bolts is very important. I agree 20 hours is too short for a 250 2 stroke clutch especially if you are not an abuser, even with stock springs. Stiffer aftermarket springs usually only become a necessity with a modified four stroke engine making way more torque. What brand of clutch pack are you using? Rekluse has a reputation for durability, though oem or any other of the respected brands should hold up. If you do indeed have some sort of factory defect, my first guess would be a warped pressure plate if you can verify the flatness of it. Uneven pressure on the plates would cause premature wear.

You don’t need to soak fibres overnight, that’s an old wives tale.