Jerry's suggestion is common practice as far as I know with any 3 speed non syncro first gear transmission. I rebuild a lot of the SM318/SM319 transmissions and most of them have chipped teeth on the L/R slider and the corresponding gear on the cluster. If you force it into first it will eventually cause serious damage.
Those gears are becoming harder to find and are pricy as well.
Clutch issues aside, it's an easy practice to get into.
Fred
