Quick question, what is the best weight of oil to use in the crankcase on a 93 KX 250. I think I've used 10w30 before, but not sure if that is the right stuff. Thanks in advance for the help.
In my 94 KX250 which is very similar I always had very good results with the following oils for the gearbox:
Mobil 10w40, Mobil 1 15w50, Type F ATF.
Whatever you use, change it as frequently as possible. I usually only go one ride and then change it.
Be careful though most 10w30 automotive oils have the "Energy Conserving" rating these days, which is a friction modifier and is supposed to not be good for the wet clutch in your bike.